Acoustic transducer with balanced performance and device for generating sound

Abstract

The acoustic transducer comprises an upper part (301) and a lower part (302), wherein a first permanent magnet (303) is in the upper part (301) and a second permanent magnet (304) is in the lower part (302). Like poles of the first and second permanent magnets (303, 304) are opposite to each other. An upper cover (306) in the upper part (301) and a lower cover (307) in the lower part (302) comprise magnetic material and define a housing around the permanent magnets (303, 304). A coil (308) generates a dynamic magnetic force under the influence of an electric current. A separation gap (309) between the edges of the upper cover (306) and the lower cover (307) is oriented to allow the lower cover (307) and the edges of the upper cover (306) to move relative to each other between different positions, wherein the positions differ in the degree to which the edges of the upper cover (306) and the lower cover (307) overlap.

Description

Technical Field

[0001] The present invention generally relates to acoustic transducers that convert electrical signals into mechanical vibrations (preferably at acoustic frequencies). The present invention specifically relates to acoustic transducers that can be used to make one or more surfaces of an electronic device act as part(s) of the conversion. Background Art

[0002] Figure 1 A known acoustic transducer is shown in a partially cut-away axonometric view without being attached to an electronic device. Figure 2 The same known acoustic transducer is shown along Figure 1 A cross section in the same plane as the cutout, wherein the attachment to the electronic device is schematically shown. Such an acoustic transducer is known, for example, from patent application document EP 3 603 110 A1.

[0003] Figure 1 and Figure 2 An acoustic transducer known in the art comprises an upper part 101 and a lower part 102 separated from each other by a horizontal gap 103. The upper part is attached to a first structural part 201 of the electronic device at its top surface. The first structural part 201 is typically a visible or at least touchable part of the electronic device, for example, a display panel of the electronic device. Its top surface 202 is visible or at least touchable to a user, so that the top surface 202 constitutes an interface with the surrounding air. The lower part 102 of the acoustic transducer is attached to a second structural part 203 of the electronic device at its bottom surface. The second structural part 203 can be, for example, part of a structural support frame of the electronic device. The structural relationship between the first structural part 201 and the second structural part 203 is used to maintain the horizontal gap 103 between the upper part 101 and the lower part 102. The gap 103 can also be filled with an elastic non-magnetic material that forms a bonding joint between the upper part 101 and the lower part 102.

[0004] The first permanent magnet is located in the upper part 101 and the second permanent magnet 105 is located in the lower part 102. Figure 1 and Figure 2 In the illustrated embodiment, the first permanent magnet 104 has a relatively flat cylindrical shape, and the second permanent magnet 105 has a relatively flat annular structure. The magnetic poles of the first permanent magnet 104 and the second permanent magnet 105 are oriented in a repelling configuration so that their like poles (S poles or N poles) are arranged opposite to each other. Therefore, the static magnetic force generated by the opposite like poles constantly pushes the upper part 101 and the lower part 102 away from each other.

[0005] The acoustic transducer includes an upper cover 106 and a lower cover 107, both of which are cup-shaped and made of magnetic material. The magnetic properties of the upper cover 106 and the lower cover 107 concentrate and guide the magnetic lines of force of the first permanent magnet 104 and the second permanent magnet 105, so that an attractive static magnetic force appears at the edge of the horizontal gap 103.

[0006] The coil 108 surrounds the second permanent magnet 105 in the lower part 102. The flat cable 109 provides an electrically conductive connection from an electronic circuit (not shown) located elsewhere in the electronic device to the coil 108. The changing current flowing through the coil 108 induces a dynamic magnetic field, which is added to the static magnetic field described above, causing the upper part 101 to move vertically relative to the lower part 102. The structural rigidity of the first structural component 201 is weaker than the structural rigidity of the second structural component 203, so the electromagnetically induced vertical movement of the upper component 101 is converted into an oscillation mode of the first structural component 201, which in turn causes the first structural component 201 to emit audible sound into the surrounding air. In short, the acoustic transducer makes the first structural component 201 act equivalent to a flat speaker.

[0007] Figure 1 and Figure 2 The inherent disadvantages of the known acoustic transducers are related to the delicate balance of repulsive and attractive static magnetic forces. In particular, the relative strength of the attractive magnetic force depends greatly on the distance between the edges of the upper cover 106 and the lower cover 107 at the gap 103. If an external force pushes the first structural member 201 downwards, for example when a user inadvertently presses the touch panel slightly harder with a fingertip, the gap 103 may temporarily close completely. This may cause the upper member 101 and the lower member 102 to come together under the influence of the enhanced attractive magnetic force, which may be so strong that this becomes a permanent condition and the transducer fails.

[0008] Figure 1 and Figure 2 A second disadvantage of the known acoustic transducers is that it is difficult to manufacture the transducer as an integral part that can be assembled separately and delivered to the manufacturer of the electronic device if the gap between the upper part and the lower part consists only of air. Usually, the upper part and the lower part of the acoustic transducer are delivered, and it is the responsibility of the device manufacturer to place and attach the upper part and the lower part sufficiently accurately in the first structural part and the second structural part of the electronic device.

[0009] A solution which would allow the acoustic transducer to be less susceptible to failure in the manner described above and which could, if desired, be manufactured as a unitary piece would be welcome. Summary of the invention

[0010] It is an object of the present invention to provide an acoustic transducer and a device for generating an acoustic signal which do not have the above-mentioned disadvantages of the prior art.

[0011] According to a first aspect, an acoustic transducer for converting an electrical signal into a mechanical vibration of an acoustic frequency is provided. The acoustic transducer comprises an upper part and a lower part. A first permanent magnet is located in the upper part and a second permanent magnet is located in the lower part. The like poles of the first permanent magnet and the second permanent magnet face each other in the direction of the axis. The acoustic transducer comprises an upper cover in the upper part and a lower cover in the lower part. The upper cover and the lower cover comprise a magnetic material and together they define a housing surrounding the first permanent magnet and the second permanent magnet. At least one coil is located in the housing and is configured to generate a dynamic magnetic force in the direction of the axis under the influence of a current flowing through the coil. The separation gap between the edges of the upper cover and the lower cover is substantially directed in the direction of the axis, allowing the edges of the lower cover and the upper cover to move relative to each other in the direction of the axis, and the positions are different in the degree to which the edges of the upper cover and the lower cover overlap in a direction perpendicular to the axis.

[0012] According to one embodiment, the upper cover has a U-shaped cross section, the first permanent magnet being located inside the ring of the U. The lower cover has a plate-shaped cross section, the outer edge of the plate defining the edge of the lower cover. The second permanent magnet is located on the side of the plate facing the inside of the U-shaped cross section of the upper cover. This involves the advantage that a properly oriented gap between the edges of the upper and lower covers can be achieved with many different construction methods.

[0013] According to one embodiment, the lower cover has a U-shaped cross section, and the second permanent magnet is located inside the ring of the U. The upper cover has a plate-shaped cross section, and the outer edge of the plate defines the edge of the upper cover. The first permanent magnet is located on the side of the plate facing the inside of the U-shaped cross section of the lower cover. This involves the point that a properly oriented gap between the edges of the upper and lower covers can be achieved with many different construction methods.

[0014] According to one embodiment, in the U-shaped cross section, the ends of the U-shaped arms comprise inwardly protruding extensions. The inner ends of the extensions define the edges of the respective covers. This has the advantage that the effects associated with magnetic field lines passing through the gap can become more pronounced.

[0015] According to one embodiment, the upper cover or the lower cover comprises a first cup part and a second cup part, each cup part having a skirt portion and an end portion. The second cup part can be in an inverted position relative to the first cup part. The skirt portions of the first cup part and the second cup part can be at least partially located inside each other, and the end portion of the second cup part has an opening, the edge of the opening defining the edge of the corresponding cover. This involves the advantage that a clearly defined extended edge of each corresponding cover can be manufactured in various detailed methods.

[0016] According to one embodiment, the skirt portions of the first cup part and the second cup part are located inside each other over most of the length of the skirt portions of the first cup part and the second cup part. The permanent magnet can be located inside the skirt portions of the first cup part and the second cup part. This has the advantage that a relatively large total wall thickness can be obtained for the corresponding cover.

[0017] According to one embodiment, the length of the skirt portion of the first cup part is greater than the length of the skirt portion of the second cup part. The permanent magnet can be located inside the skirt portion of the first cup part, and the first permanent magnet and the second cup part can be stacked inside the skirt portion of the first cup part. This involves the advantage that the permanent magnet can be attached to the first cup part before attaching the second cup part.

[0018] According to one embodiment, the upper and lower parts comprise sheets of magnetic material stacked between end portions of the permanent magnet first cup part. This involves the advantage of increasing the thickness of the magnetic material in the corresponding part of the structure.

[0019] According to one embodiment, the upper cover and the lower cover include a first cup part and a second cup part, each cup part having a skirt portion and an end portion. The second cup part can be in a similarly oriented position relative to the first cup part and is located inside the first cup part. The skirt portion of the second cup part can include a perforated area of ​​the skirt portion at an intermediate longitudinal level of the skirt portion. The skirt portion of the second cup part includes a solid area at its end opposite to the end portion, which solid area defines the edge of the corresponding cover. This involves the advantage that metal processing of the corresponding parts can be completed before adding the first permanent magnet.

[0020] According to one embodiment, the upper or lower cover comprises a first cup part having a skirt portion, which is closed at one end by an end portion and is open at the other end. The respective cover may comprise a gasket part having an outer edge and an inner edge, wherein the inner edge defines an opening smaller than the inner dimensions of the skirt portion. The gasket part may be attached to the open end of the skirt portion concentrically with the first cup part, such that the inner edge of the gasket part defines the edge of the respective cover. This involves the advantage that the upper part edge can be produced with very precise dimensions.

[0021] According to one embodiment, the acoustic transducer comprises a support member configured to resist relative movement of the upper and lower parts in a direction perpendicular to the axis while allowing relative movement of the upper and lower parts in the direction of the axis. This has the advantage that the size of the gap can be accurately maintained.

[0022] According to one embodiment, the support member comprises a multi-branched helical spring, the central portion of which is attached to one of the upper and lower parts, and the ends of which are attached to the other of the upper and lower parts. This has the advantage that the support member is relatively easy to manufacture and attach to the rest of the acoustic transducer structure.

[0023] According to one embodiment, the support member comprises a foil attached to the upper and lower parts and bridging the separation gap. This involves the advantage that very thin support members can be used, reducing the overall height of the acoustic transducer.

[0024] According to one embodiment, at least a portion of the foil constitutes a flexible printed circuit for conducting electrical signals to the at least one coil. This involves the advantage that one structural component can be used for a dual purpose, reducing the total number of components in the acoustic transducer structure.

[0025] According to a second aspect, a device for producing sound is provided. The device comprises an electronic device having a first structural component and a second structural component, and at least one acoustic transducer of the above kind. An upper component of the acoustic transducer is attached to the first structural component, and a lower component of the acoustic transducer is attached to the second structural component of the electronic device. As part of the electronic device, a circuit is configured to feed an electrical signal to the at least one coil of the acoustic transducer.

[0026] According to one embodiment, the first structural component comprises a visible outer surface of the electronic device, such as a display of the electronic device. This has the advantage that a separate loudspeaker can be omitted, so that another structural component of the electronic device also serves as a sound emitter.

[0027] According to one embodiment, the second structural component comprises a part of a structural support frame of the electronic device. This involves the advantage that it is relatively easy to provide sufficient structural rigidity to support the lower part of the acoustic transducer.

[0028] According to one embodiment, the upper part of the acoustic transducer has a first lateral dimension on the side where the upper part is attached to the first structural part. The device may include a first substantially inelastic attachment member located between the upper part and the first structural part for transferring the movement of the upper part in the direction of the axis into the first structural part. The first attachment member may have a second lateral dimension that is smaller than the first lateral dimension. This involves the advantage that a smaller part of the first structural part of the electronic device needs to remain rigid.

[0029] According to one embodiment, the device comprises a second substantially elastic attachment member between those parts of the upper part and the first structural part that are not covered by the first attachment member for stabilizing the upper part against tilting relative to the first structural part. This has the advantage that the attachment of the acoustic transducer can be stabilized without impairing its ability to transmit oscillations to the first structural part of the electronic device.

[0030] According to one embodiment, the second attachment member comprises an elastically deformable cushioning material and / or a spring branch, which extends on the first structural component further than the first lateral dimension of the upper part. This involves the advantage that the desired support characteristics can be achieved with a variety of implementation possibilities.

[0031] According to one embodiment, the device comprises a support sheet between the upper part and the first structural part for matching the local elastic properties of the first structural part with the movement transmitted to the first structural part by the upper part. This has the advantage of better matching the local elastic properties of the first structural part with the movement transmitted to it by the upper part. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings are included to provide a further understanding of the present invention and constitute a part of this specification. The accompanying drawings illustrate embodiments of the present invention and together with the description help explain the principles of the present invention. In the drawings:

[0033] Figure 1 A known acoustic transducer is shown,

[0034] Figure 2 A known acoustic transducer is shown,

[0035] Figure 3 shows an acoustic transducer according to an embodiment,

[0036] Figure 4 shows an acoustic transducer according to an embodiment,

[0037] Figure 5 shows the resultant static magnetic force as a function of vertical motion in various configurations,

[0038] Figure 6 shows an acoustic transducer according to an embodiment,

[0039] Figure 7 shows an acoustic transducer according to an embodiment,

[0040] Figure 8 shows an acoustic transducer according to an embodiment,

[0041] Fig. 9 shows an acoustic transducer according to an embodiment,

[0042] FIG. 10 shows an acoustic transducer according to an embodiment,

[0043] FIG. 11 shows the acoustic transducer of FIG. 10 in an exploded view,

[0044] FIG. 12 shows an acoustic transducer according to an embodiment,

[0045] Fig.13 shows an acoustic transducer according to an embodiment,

[0046] Fig.14 An example of an elastic support member is shown,

[0047] Fig.15 shows an acoustic transducer according to an embodiment,

[0048] Fig.16 shows an acoustic transducer according to an embodiment,

[0049] Fig.17 shows an acoustic transducer according to an embodiment,

[0050] Fig.18 shows an acoustic transducer according to an embodiment,

[0051] Fig.19 An acoustic transducer according to one embodiment is shown, and

[0052] Fig. 20 Shown in a partially exploded view Fig.19 The acoustic transducer in. DETAILED DESCRIPTION

[0053] Figure 3 An acoustic transducer according to one embodiment is shown in a partially cut-away axonometric view. Figure 4 shows the same acoustic transducer along Figure 3 A cross section in the same plane as the cutout, schematically showing the attachment to the electronic device.

[0054] The acoustic transducer comprises an upper part 301 and a lower part 302. Here and in all other parts of this article, terms related to directions such as "upper" or "lower" are merely illustrative names for comparison with the drawings. Such terms should not be interpreted as limiting the applicability or use of the corresponding parts or features in any particular direction in any actual implementation of the embodiments. Another important overview is that even though many of the embodiments shown in the drawings are rotationally symmetric and have an overall cylindrical form, this is only to make the drawings easier to read. The cylindrical form is by no means restrictive, and most of the structures shown can have other forms, such as triangles, rectangles, hexagons or other polygons. This is particularly applicable to the overall profile of the acoustic transducer, and the overall profile of the cover component, permanent magnet and coil caused thereby.

[0055] Figure 4 The general role of the upper part 301 and the lower part 302 in the device for producing sound is schematically shown. It is assumed that the electronic device comprises a first structural part 401 and a second structural part 402. The upper part 301 of the acoustic transducer is attached to the first structural part 401 and the lower part 302 of the acoustic transducer is attached to the second structural part 402 of the electronic device.

[0056] The first permanent magnet 303 is located in the upper part 301, and the second permanent magnet 304 is located in the lower part 302. The magnetic poles of the first permanent magnet 303 and the second permanent magnet 304 are indicated by oblique hatching in the figure. The like-named magnetic poles of the first permanent magnet 303 and the second permanent magnet 304 face each other in the direction of the axis 305, which also represents the direction in which the "upper" and "lower" markings are generated. The like-named magnetic poles refer to the north pole or the south pole, so that the S pole of the first permanent magnet 303 faces the S pole of the second permanent magnet 304, or the N pole of the first permanent magnet 303 faces the N pole of the second permanent magnet 304. As a result, the basic static magnetic interaction between the first permanent magnet 303 and the second permanent magnet 304 is a repulsive force in the direction of the axis 305.

[0057] The acoustic transducer comprises an upper cover part 306 in the upper part 301 and a lower cover part 307 in the lower part 302. The upper cover 306 and the lower cover 307 comprise magnetic materials, and the most important result is that the upper cover 306 and the lower cover 307 are able to confine a large part of the magnetic field lines of the first permanent magnet 303 and the second permanent magnet 304 within their materials. The upper cover 306 and the lower cover 307 together define an enclosure around the first permanent magnet 303 and the second permanent magnet 304.

[0058] At least one coil 308 is located in the housing. In the present embodiment, the coil 308 is generally annular and is placed around the second permanent magnet 304 in the same plane as the second permanent magnet 304. In other words, the axis 305 also represents the central axis of the coil 308. There are other possibilities for placing the coil in the housing formed by the upper cover 306 and the lower cover 307, and they will be described in more detail later in this article. The coil 308 is configured to generate a dynamic magnetic force in the direction of the axis 305 under the influence of the current flowing through it. In the device for generating sound, the electronic device includes a circuit that is configured to feed an electrical signal (i.e., current of different forms and magnitudes) into the coil 308 of the acoustic transducer.

[0059] The acoustic transducer includes a separation gap 309 between the edges of the upper cover 306 and the lower cover 307. The separation gap 309 generally points in the direction of the axis 305. This is consistent with Figure 1 and Figure 2 This is significantly different from previously known acoustic transducers in which the separation gap is substantially perpendicular to the central vertical axis of the structure. Figure 4 As shown in the enlarged view of the lower part, the separation gap 309 allows the edges of the lower cover 307 and the upper cover 306 to move relative to each other between different positions along the direction of the axis 305. These positions differ from each other in the degree to which the edges of the upper cover 306 and the lower cover 307 overlap in the direction perpendicular to the axis 305. For example, Figure 4 In the leftmost partial enlarged view, the edges of the upper cover 306 and the lower cover 307 overlap to the extent indicated by arrow 404, while in the middle and rightmost partial enlarged views they overlap to the extent indicated by arrows 404 and 405, respectively.

[0060] Figure 5 A comparison of the resultant static magnetic force in three example structures of an acoustic transducer is shown. The horizontal axis represents the vertical separation of the upper and lower parts of the transducer, and the vertical axis qualitatively shows whether the resultant static magnetic force is repulsive or attractive. The resultant static magnetic force is the vector sum of the attractive and repulsive static magnetic force components, and for simplicity, only the vertical direction is considered. The attractive static magnetic force component essentially comes from a portion of the magnetic field whose magnetic lines of force are confined to the magnetic material of the upper cover 106 and the lower cover 107. The repulsive static magnetic force component essentially comes from a portion of the magnetic field whose magnetic lines of force occupy the free space between like poles facing each other in the middle of the acoustic transducer structure.

[0061] Figure 5 The solid line curve 501 corresponds to Figure 1 and Figure 2The previously known acoustic transducer shown and described in the background section. In such a structure, the zero point of the vertical spacing (i.e., the zero point of the horizontal axis) is where the edges of the upper cover 106 and the lower cover 107 bite each other, i.e., the gap 103 is completely closed. There is a nominal design point 502 at which the resultant static magnetic force is zero. Figure 5 As shown, the resultant static magnetic force represented by curve 501 is attractive over the entire range between the nominal design point 502 and the zero point. This is because in the known structure, at small vertical separations, the attractive static magnetic force component exceeds the repulsive static magnetic force component. The attractive resultant static magnetic force is largest at zero vertical distance. This illustrates the problem with the known structure mentioned above: if external forces (such as those caused by a careless user) press the components of the acoustic transducer too close to each other, they may not be able to return to the nominal design point 502, even if elastic forces caused by the structural components of the electronic device try to bring them back there. The elastic force may be too weak to overcome the strong magnetic attraction at zero distance (or other very short distances).

[0062] Figure 5 The dashed curve 503 corresponds to Figure 3 and Figure 4 The acoustic transducer structure shown. In this case, the zero point of the vertical spacing refers to: the lower part 302 of the acoustic transducer is so deep in the upper part 301 that the second permanent magnet 304 or the coil 308 or both contact the first permanent magnet 303. Although the nominal design point 502 of the curve 503 is shown as coinciding with the nominal design point of the curve 501, this is only for illustrative comparison and does not mean that the vertical spacing corresponding to the nominal design point should exist at an equal vertical spacing in all cases.

[0063] Curve 503 shows Figure 3 and Figure 4 The structure shown has a spontaneous tendency to seek equilibrium at the nominal design point 502. If the vertical separation is small, the repulsive static magnetic force component dominates and attempts to push the upper and lower parts 301 and 302 further away from each other towards the nominal design point 502. If the vertical separation is large, the attractive static magnetic force component dominates and attempts to pull the upper and lower parts 301 and 302 closer together, also towards the nominal design point 502. There may be another equilibrium point at a larger vertical separation, i.e., where the curve 503 crosses the horizontal axis again, but this is typically at a large distance that the structure of the electronic device cannot reach in any case.

[0064] Advantageously, the acoustic transducer and its attachment to the electronic device are designed so that when no current flows through the coil, the vertical spacing between the upper and lower components is at or near the nominal design point 502. This is because the resultant static magnetic force has its minimum absolute value near the nominal design point 502, so the relatively small dynamic magnetic force generated by the current flowing through the coil is already sufficient to cause relative movement of the upper and lower components (i.e., the dynamic magnetic force does not need to oppose any large static magnetic force). After all, repeated relative movement like that is how the acoustic transducer invokes oscillation modes in appropriate structural components of the electronic device and thereby the emission of acoustic signals. It is advantageous if a small current is sufficient because it means relatively low power consumption. For the same reason, it is advantageous to design the structural components of the electronic device so that when the acoustic transducer is at its nominal design point 502, the resultant force generated by the static elastic force is also zero.

[0065] As noted above, the static magnetic component of attraction is essentially derived from the portion of the magnetic field whose magnetic lines of force are confined to the magnetic material of the upper and lower covers 106, 107. The relative strength of the static magnetic component of attraction depends on the degree to which the edges of the upper and lower covers 306, 307 overlap (see Figure 4 404, 405 and 406 in FIG. 4). Figure 3 and 4 Simulations and experiments were performed on each practical implementation of the illustrated principle to find the location of the nominal design point 502, ie, the vertical spacing where the edges of the upper cover 306 and the lower cover 307 just coincide appropriately, so that the attractive and repulsive static magnetic force components are equal.

[0066] An alternative embodiment may be provided in which the resultant static magnetic force never becomes attractive, but instead follows Figure 5 504 in FIG. Such an embodiment can be constructed by determining the dimensions of the cover edge and the gap accordingly, for example by simulation and / or experimentation. Figure 5 Such an "always repelling" embodiment may have the advantage that the resultant static magnetic force changes only relatively slowly with distance, as schematically shown by curve 504. The static mechanical forces generated by the structural components of the electronic device may be used to properly balance the structure and maintain a constant repelling force to prevent the upper and lower components of the acoustic transducer from moving further from each other than is practical.

[0067] Figure 3 and Figure 4are considered to be schematic features of various components of the acoustic transducer, rather than taking any precise position in actual implementation. In general, it can be said that it is most preferred that the upper cover 306 has a U-shaped (or, in the orientation shown in the figure, an inverted U-shaped) cross-section. The first permanent magnet 303 is located inside the U-shaped ring. In the U-shaped cross-section, the ends of the arms of the U-shape include extensions 403 that protrude inwardly. The inner ends of these extensions 403 define the edges of the upper cover 306, which is important when considering the degree of overlap with the edges of the lower cover. The lower cover 307 has a plate-shaped cross-section, and the outer edge of the plate defines the corresponding edge of the lower cover 307. The second permanent magnet 304 is located on the side of the plate facing the inside of the U-shaped cross-section of the upper cover 306.

[0068] Next, refer to Figure 6 to Figure 1 2 describes some possible, alternative practical implementations. These are along the lines of including Figure 3 and 4 A cross section is shown in the plane of the axis 305. Here again, it is reminded that although cylindrical symmetry is shown in the figures, this is not necessary but is only an example. Other forms, such as polygons with different numbers of angles are also possible.

[0069] Figure 6 An acoustic transducer is shown, wherein the upper cover comprises a first cup member 601 and a second cup member 602. Each cup member has a skirt portion and an end portion, so that in a corresponding U-shaped cross section, the arms of the U-shape represent the skirt portion and the bottom of the U-shape represents the end portion. The second cup member 602 is in an inverted position relative to the first cup member 601. Figure 6 In FIG. 6 , this is shown such that the cross-section of the second cup member 602 is a true U-shape, while the cross-section of the first cup member 601 is an inverted U-shape. The skirt portions of the first cup member 601 and the second cup member 602 are located inside each other over most of their length; specifically, in FIG. Figure 6 In the embodiment of the present invention, the skirt portion of the second cup member 602 is located inside the skirt portion of the first cup member 601. The end portion of the second cup member 602 has an opening, and the edge of the opening defines the above reference Figure 3 and Figure 4 Describes the edge of the upper cover.

[0070] Figure 7 An acoustic transducer is shown which is otherwise similar to Figure 6 The acoustic transducer in is similar, but the upper component includes a sheet of magnetic material 701 stacked between the first permanent magnet 303 and the end portion of the first cup component 601.

[0071] Figure 8An acoustic transducer is shown in which the skirt portion of the second cup member 802 is significantly smaller than the skirt portion of the first cup member 601. Therefore, the skirt portions of the first cup member 601 and the second cup member 802 are only partially located inside each other. Specifically, the entire skirt portion of the second cup member 802 is located inside a portion of the skirt portion of the first cup member 601. Fig. 9 The acoustic transducer is similar to Figure 8 The acoustic transducer is similar to Fig. 9 The upper middle part includes a magnetic material sheet 701 stacked between the first permanent magnet 303 and an end portion of the first cup part 601 .

[0072] on the one hand Figure 6 and Figure 7 The acoustic transducer and on the other hand Figure 8 and Fig. 9 The acoustic transducer of has a difference in the relative size of the first permanent magnet 303 and the second cup member 602 or 802. Figure 6 and Figure 7 In the embodiment of the present invention, the first permanent magnet 303 is located in the skirt portion of the first cup part 601 and the second cup part 602. Figure 8 and Fig. 9 In the embodiment of the present invention, the length of the skirt portion of the first cup member 601 is greater than the length of the skirt portion of the second cup member 802, and the first permanent magnet 303 is only located in the skirt portion of the first cup member 601. Figure 8 and 9 In the embodiment of FIG. 8 , the first permanent magnet 303 and the second cup member 802 are actually stacked within the skirt portion of the first cup member 601 .

[0073] Figures 6 to 9 The embodiments shown differ somewhat in the order in which their upper parts are assembled during the manufacturing process. Figure 8 and 9 In the embodiment of , it is relatively easy to attach the first permanent magnet 303 to the first cup member 601 (possibly with an additional sheet of magnetic material 701 stacked between them), and only thereafter add the second cup member 802 and attach the skirt portions of the first and second cup members together. Figure 6 and Figure 7 The embodiment of FIG. 6 is assembled in a similar sequence, however the first permanent magnet 303 will need to be carefully aligned with the first cup member 601 during the attachment process so that the skirt portion of the second cup member 602 can thereafter slide around it. Figure 6 and 7 A more advantageous sequence of embodiments may be to first attach the first permanent magnet 303 (and possibly also the additional magnetic material piece 701 ) to the second cup part 602 and then only attach this whole to the first cup part 601 .

[0074] Figures 10 and 11 show an acoustic transducer according to another alternative embodiment. Figure 10 shows the acoustic transducer in an assembled structure, and Figure 11 shows the parts of the acoustic transducer that are partially separated from each other. Also in this embodiment, the upper cover includes a first cup part 1001 and a second cup part 1002, each of which has a skirt portion and an end portion. In this embodiment, the second cup part 1002 is in a position oriented similarly to the first cup part 1001 (both are inverted U-shaped in cross section) and is located inside the first cup part 1001. The skirt portion of the second cup part 1002 includes a perforated area 1101 of the skirt portion at its middle longitudinal level. In addition, the skirt portion of the second cup part 1002 includes a solid area 1102 at one end of the skirt portion opposite to the end portion of the second cup part 1002.

[0075] The solid area 1102 defines the edge of the upper cover, which has been shown in the above reference diagram. Figure 3 and 4 This is the result of the perforated area 1101 removing such a large proportion of the solid material that the majority of the magnetic flux that would otherwise be confined in the magnetic material of the second cup 1002 must pass through the perforated area 1101 via the skirt portion of the first cup 1001 .

[0076] An advantage of the embodiment shown in FIGS. 10 and 11 is that, except for the first permanent magnet 303 , all manufacturing stages of the upper cover (including the forming and attaching together of the magnetic materials) can be completed before attaching the first permanent magnet 303 .

[0077] Figure 12 shows an acoustic transducer according to another alternative embodiment. In Figure 12, the upper cover includes a first cup member 1201 having a group portion, which is closed by an end portion at one end (above) and is open at the other end (below). In this way, the first cup member 1201 is very similar to the first cup member in the other embodiments described above. However, there is no second cup member in the embodiment of Figure 12. Instead, the upper cover includes a gasket member 1202 having an outer edge and an inner edge. The inner edge defines an opening that is smaller than the inner dimension of the skirt portion in the first cup member 1201. The gasket member 1202 is attached to the open end of the skirt portion of the first cup member 1201 concentrically with the first cup member 1201. Therefore, the inner edge of the gasket member 1202 also defines the above reference Figure 3 and Figure 4 Describes the edge of the upper cover.

[0078] If desired, the embodiment shown in Figure 12 may add an additional sheet of magnetic material between the end portion of the first cup member 1201 and the first permanent magnet 303. The embodiment shown in Figure 12 includes the additional advantage that because the significant edge of the upper cover is defined only by the gasket member 1202, the thickness, shape and other features of the edge may be selected more freely than in many other embodiments.

[0079] Can Figure 6 to 1 2. For example, in a similar Figures 6 to 9 In the embodiment of the invention, the inner diameter of the skirt portion can be chosen in the opposite way, so that the skirt portion of the first cup part will enter the skirt portion of the second cup part. Furthermore, it is not necessary to flatten the upper cover of the two separate parts at the beginning. Even if it is desired that the first permanent magnet fills its available space to the maximum extent, it is possible to first manufacture the cup-shaped upper cover with a straight skirt portion, attach the first permanent magnet in place, and only thereafter bend the free edge of the skirt portion inwards to produce the shape shown in the above reference diagram. Figure 3 and 4 Describes the edge of the upper cover.

[0080] exist Figure 6 to Figure 1 In the embodiment of 2, the various cup components can be made of, for example, a thin sheet of magnetic metal by stamping or pressing. The thinner the metal sheet, the easier it is to press neatly and accurately into the cup shape. However, since the purpose of the upper and lower covers is to confine the magnetic lines of force of the magnetic field involved, it is disadvantageous to make them arbitrarily thin: thin layers of material are not as effective as thick layers of material in confining the magnetic lines of force. For example, in Figure 7 and 9 In the embodiment of the invention, the purpose of the additional magnetic material sheet 701 is to increase the material thickness, thereby improving the ability of the topmost portion of the upper cover to limit the magnetic field lines. Aiming for the maximum total thickness of the magnetic material also advocates similar Figure 6 , 7 , 10 and 11, wherein the skirt portions of the two cup parts are located inside each other over most of their lengths. For example, in a similar Figure 6 to 1 2, the wall thickness of any single piece of magnetic material stamped or pressed from a metal sheet may be in the order of 0.2 mm to 1.0 mm, preferably between 0.5 mm and 0.75 mm, including both ends.

[0081] With sheet metal as a starting point, pressing or stamping as a manufacturing method are not the only possible options. The cup part, or indeed any mechanical assembly of the upper and lower parts of the acoustic transducer, can be manufactured, for example by milling from a blank or by additive manufacturing methods such as 3D printing.

[0082] The vertical spacing between the topmost portions of the first permanent magnet and the second permanent magnet or coil (or both, if they are on the same horizontal plane) may be of the order of a few hundred micrometers, for example Figure 5 The nominal design point mentioned in the description of is 400 microns. In operation, i.e. when oscillations at the acoustic frequency are generated, the relative vertical movement of the upper and lower parts may be much smaller than this, on the order of only a few microns, or on the order of tens of microns at the lowest expected frequencies. Gap 309 (see Figure 3 The shortest distance between the edges of the upper and lower parts at ) is advantageously of the order of tens or hundreds of microns, for example between 50 and 500 microns. A small gap is advantageous in terms of making the static magnetic force component of attraction effectively contribute to the desired mode of operation, but the precision achievable by the manufacturing method may set a lower limit on the goal of a small gap.

[0083] With regard to the intended operation of the acoustic transducer, it is advantageous to allow the upper and lower parts to move very freely relative to each other in the vertical direction (the direction of the axis 305) while preventing them from moving in the horizontal direction. Advantageously, the acoustic transducer may include a support member configured to resist relative movement of the upper and lower parts 301, 302 in a direction perpendicular to the axis 305 while allowing relative movement of the upper and lower parts 301, 302 in the direction of the axis 305.

[0084] Fig.13 A device for producing sound is schematically shown. The device comprises an electronic device having a first structural component 402 and a second structural component 402, and an acoustic transducer of the type described above. Figure 4 A schematic diagram of is used for the acoustic transducer to emphasize that the example embodiment is not limited to any particular practical implementation of the acoustic transducer. The upper part 301 of the acoustic transducer is attached to the first structural part 401 and the lower part 302 of the acoustic transducer is attached to the second structural part 402 of the electronic device. Although Fig.13 It is not shown in the figure, but it is assumed that the electronic device comprises a circuit which is configured to feed an electrical signal into at least one coil of the acoustic transducer.

[0085] The support member 1301 is Fig.13 As explained above, the support member 1301 is configured to resist relative movement of the upper member 301 and the lower member 302 in a direction perpendicular to the axis 305, while allowing relative movement of the upper member 301 and the lower member 302 in the direction of the axis 305. In this embodiment, the support member 1301 is a part of the device that attaches the lower member 302 to the second structural member 402 of the electronic device. More specifically, in this embodiment, the support member 1301 is stacked between the lower member 302 and the second structural member 402.

[0086] Fig.14 An example of the support member 1301 is shown. According to this embodiment, the support member 1301 includes a multi-branched coil spring. Fig.13 In the manner shown, the central portion 1401 of the multi-branched helical spring 1301 is attached to the lower part 302, and the ends 1402 of the multi-branched helical spring 1301 are attached to the upper part 301. It is assumed that the branches of the helical spring 1301 are very rigid in the radial direction, so that they effectively prevent the undesired relative movement of the upper part 301 and the lower part 302 in the direction perpendicular to the axis 305. At the same time, the branches of the helical spring 1301 are very ductile in the lateral direction, so that they have almost no resistance to the relative movement of the upper part 301 and the lower part 302 in the direction of the axis 305. Instead of the multi-branched helical spring, a circular, cross-shaped or star-shaped leaf spring can be used as the supporting member.

[0087] Fig.15 An alternative embodiment is shown in which the support member comprises a foil 1501 attached to the upper part 301 and the lower part 302 and bridging the gap 309. It is assumed that the foil 1501 exhibits very little stretching under forces parallel to the foil itself, while it can bend relatively easily under forces perpendicular to the foil. Although any relative vertical displacement of the upper part 301 and the lower part 302 also requires the foil 1501 to stretch, at least in a mathematically precise sense, the magnitude of the required vertical displacement may be in the order of microns, while the width of the gap 309 may be hundreds of microns. The relative size of these dimensions means that the amount of stretching that the foil 1501 must exhibit to allow such vertical displacement is very small. Fig.15 It is also shown how, in this exemplary embodiment, the first structural component 1502 and the second structural component 1503 are located below the foil 1501 (or at least have some portions extending below the foil 1501 ).

[0088] According to an exemplary embodiment, at least a portion of the foil 1501 may constitute a flexible printed circuit for conducting electrical signals to at least one coil 308 in the acoustic transducer. In this case, at least a portion of the foil 1501 will extend further from the acoustic transducer, and / or Fig.15 One or more of the components of the illustrated structures will have the necessary conductive vias for conducting electrical signals through those components.

[0089] The structural components of the electronic device must be formed so that they do not unnecessarily interfere with the intended relative vertical movement of the upper and lower parts of the acoustic transducer. Fig.13In the embodiment shown, this has been achieved by having the second structural member 402 include a raised portion 1302 to which the acoustic transducer is attached by an attachment layer 1303, which may be, for example, glue or tape. The attachment layer 1303 may also include other forms of attachment, such as ultrasonic welding.

[0090] exist Fig.13 As mentioned above Figure 4 One possibility is that the first structural component 401 comprises a visible outer surface of the electronic device, such as a display of the electronic device. The second structural component 402 may comprise, for example, a part of a structural support frame of the electronic device.

[0091] The purpose of an acoustic transducer is to convert the vertical movement of its upper part into an oscillation mode of a structural part of the electronic device in order to produce sound. In all cases, the upper part of the acoustic transducer is attached to such a structural part. How this attachment is achieved has a great influence on the efficiency and the subjective quality level of the sound production. This applies to all acoustic transducers in general, but also to Figure 1 and Figure 2 The acoustic transducers shown and those described in the background section above. The oscillation modes induced in the structural components of electronic devices can be very complex, including multiple two-dimensional modes with multiple wavelengths in both dimensions. A basic trend is that the higher the frequency of the sound to be generated, the more complex the oscillation modes involved in generating it.

[0092] For example, refer to the above Figure 1-4 In the embodiments described in , 6-13 and 15, the characteristic lateral dimension of the upper surface of the upper component can be about 15-20 mm. If the acoustic transducer exhibits cylindrical symmetry, the upper surface of the upper component is circular, so its characteristic lateral dimension is its diameter. Due to the close stacking structure of the end portion of the cup component, possible additional magnetic material sheets and the first permanent magnet, the upper component can be relatively stiff. If it is rigidly attached to the first structural component of the electronic device over the entire upper surface, this means that the corresponding part of the first structural component of the electronic device will remain completely rigid, excluding the occurrence of any such oscillation mode in which the circular portion oscillates in other ways besides vertically back and forth as a whole. In some cases, for example, if the display (or other first structural component) of the electronic device is small, this may result in suboptimal audio quality.

[0093] It would be advantageous to provide a device for producing sound which does not have the above disadvantages. The device should include an electronic device having a first structural part and a second structural part, and an acoustic transducer, the upper part of the acoustic transducer being attached to the first structural part and the lower part of the acoustic transducer being attached to the second structural part. As part of the electronic device, an electronic circuit should be provided, which is configured to feed an electrical signal into at least one coil of the acoustic transducer.

[0094] According to one aspect, following Fig.16 The above advantageous objectives are achieved by using the principles schematically shown in Figure 3 and 4 An acoustic transducer of the type described is used as an example, but Fig.16 The principle shown also applies to the previous reference Figure 1 and 2 An acoustic transducer of the type described.

[0095] exist Fig.16 In the principle of the invention, the upper part 301 of the acoustic transducer has a first lateral dimension D1 on the side where it is attached to the first structural part 401 of the electronic device. The device comprises a substantially non-elastic first attachment member 1601 between the upper part 301 and the first structural part 401 for transferring the movement of the upper part 301 in the direction of the axis 305 into the first structural part 401. The first attachment member 1601 has a second lateral dimension D2 which is smaller than the first lateral dimension D1.

[0096] The first attachment member 1601 may be a separate component, such as a metal or hard plastic disk, placed between the upper component 301 and the first structural component 401. Alternatively, it may be an integral part of the upper component 301, for example if the cup-shaped exterior of the upper component 301 is machined from a solid blank, leaving a raised portion in its center.

[0097] The effect of using a slightly smaller attachment member 1601 between the upper component 301 and the first structural component 401 is that only the portion of the first structural component 401 having the characteristic lateral dimension D2 remains rigid. All other portions of the first structural component 401 can participate in any oscillation mode that produces the desired sound.

[0098] exist Fig.16 In the embodiment shown, the device comprises a substantially resilient second attachment member 1602 located between the upper component 301 and those portions of the first structural component 301 not covered by the first attachment member 1601. The second attachment member 1602 is provided to stabilize the upper component 301 against tilting relative to the first structural component 401. Fig.17An alternative embodiment is shown in which a different kind of second attachment member 1701 is provided for the same purpose. Fig.16 In the embodiment, the second supporting member 1602 is made of elastically deformable cushioning material, and Fig.17 In the embodiment, the second support member 1701 comprises a spring branch which extends on the first structural member 401 further than a characteristic lateral dimension D1 of the upper member 301 .

[0099] Fig.16 and 17 Another optional feature shown is a support sheet 1603 placed between the upper member 301 and the first structural member 401 of the electronic device. Although the support sheet 1603 is shown here for use with the first and second attachment members, it can also be used in embodiments without them (see, for example, Fig.13 The purpose of the support sheet is to match the local elastic properties of the first structural component 401 with the movement transmitted to the first structural component by the upper part 301. In particular, if the first attachment member 1601 is used, it may happen that the first structural component 401 may become susceptible to excessive point loads, so the support sheet 1603 can be used to ensure its sufficient structural strength.

[0100] Fig.18 An alternative embodiment is shown in which a support post 1801 extends along the central axis of the acoustic transducer, through its lower member 302, to the inner surface of the upper cover in the upper member 301.

[0101] In most of the above embodiments, the upper cover has a U-shaped cross section, although as mentioned above, calling it an "upper cover" refers only to the direction shown in the figures. Any of the above acoustic transducers can be turned upside down, so that the cover with a U-shaped cross section can be considered as the "lower" cover.

[0102] Fig.19 An acoustic transducer according to one embodiment is shown. Fig. 20 The same acoustic transducer is shown in a partially exploded view. The acoustic transducer according to the present embodiment includes an upper part 301 and a lower part 302. A first permanent magnet 303 is located in the upper part 301, and a second permanent magnet 304 is located in the lower part 302. The like poles of the first permanent magnet 303 and the second permanent magnet 304 face each other in the direction of the axis 305. An upper cover 306 is provided in the upper part 301, and a lower cover 307 is provided in the lower part 302. The upper cover 306 and the lower cover 307 include magnetic material and together define a housing surrounding the first permanent magnet 303 and the second permanent magnet 304. A coil 308 is located in the housing, here in the lower part 302. The coil 308 is configured to generate a dynamic magnetic force in the direction of the axis 305 under the influence of a current flowing therethrough.

[0103] The separation gap 309 between the edges of the upper cover 306 and the lower cover 307 is substantially directed in the direction of the axis 305. It allows the edges of the lower cover 307 and the upper cover 306 to move relative to each other between different positions along the direction of the axis 305. In particular, the positions differ in the degree to which the edges of the upper cover 306 and the lower cover 307 overlap in a direction perpendicular to the axis 305.

[0104] exist Fig.19 and 20 In the embodiment of the invention, the lower cover 307 has a U-shaped cross section, and the second permanent magnet 304 is located inside the loop of the U. In this very simple embodiment, the ends of the arms of the U do not include any inwardly protruding extensions having inner ends defining the edges of the lower cover 307. Such inwardly protruding extensions are not even required by the above definition, according to which the possible relative positions of the upper and lower covers differ in the extent to which the edges of the covers overlap in the vertical direction. The definition is satisfied here, therefore, if the upper part 301 is from Fig.19 If the position shown is moved downward, the larger portion of the edge of the upper cover 306 directly crosses the gap 309 and faces the interior of the lower cover 307. Fig.19 When the upper member 301 moves upward, it moves out of the “cup” formed by the lower cover 307 , so that a smaller portion of the edge of the upper cover 306 directly crosses the gap 309 to face the interior of the lower cover 307 .

[0105] It can be noted that, similarly, although Figure 3-4 The embodiments shown in , 6-13 and 15-18 have inwardly protruding extensions at the ends of the arms of the U-shaped cross-section of the upper cover, but in those embodiments, the structure can also be slightly simplified to resemble Fig.19 and 20 The inwardly protruding extensions may help achieve a desired balancing effect on the characteristics of the acoustic transducer, but they are not necessary to achieve the operating principles described herein.

[0106] Instead, an inwardly projecting extension may be added to Fig.19 and 20 The ends of the arms of the U-shaped cross-section of the lower cover 307. As an example, the previously described Figure 6-1 Any of those structural solutions regarding the U-shaped cross-section of the upper cover introduced in 2.

[0107] Fig.19 and 20An additional feature shown is an opening 1901 located in the center of the lower cover 307. Similar openings centered around the axis 305 can be used in any upper and lower covers in all embodiments. Such an opening can be used to produce a favorable effect in guiding the magnetic field lines of the permanent magnets in an optimal manner.

[0108] Any features previously described that do not directly depend on which of the upper and lower covers has a U-shaped cross section may apply to Fig.19 and 20 Examples of such features include, but are not limited to, support members 1301 and 1501, Fig.13 and 16 -18 shown in the attachment technique, even Fig.15 The attachment technique shown is simple if the structural member shown as 1502 is placed on Fig.19 and 20 The top of the acoustic transducer (refer to the orientation shown in the figure).

[0109] An interesting additional area of ​​embodiments involves using the device described above as an acoustic transducer to construct a vibrating device for purposes other than emitting sound. As a first example, the vibrating device can be used to generate a vibrating alarm, similar to the way many portable communication devices use electric motors connected to eccentric weights. To this end, the lower part of the device can be attached to a structural component of the electronic device, just as in the above embodiments. Instead of attaching the upper part to the inside of a display or other structural component, the upper part of the device can be free, perhaps with some additional weights attached to it, in order to achieve one or more suitable mechanical resonant frequencies.

[0110] As another example, a vibration device may be used to produce a haptic effect as part of a user interface involving touch. It has been found that the human sense of touch may be deliberately misled, for example, so that a person gets the sensation of pressing a key even though in reality he or she receives only haptic feedback in the form of a suitably designed short-term waveform involving oscillations of relatively high frequency. For this purpose, the attachments to the structural components of the electronic device may be similar to those described above with reference to the various figures, but with the elastic properties of the components and the electronic signals to the coils designed for optimization of the haptic effect.

[0111] It is obvious to those skilled in the art that, as technology advances, the basic idea of ​​the present invention can be implemented in various ways. Therefore, the present invention and its embodiments are not limited to the above examples, on the contrary, they can be varied within the scope of the claims. For example, even if only one coil is described in the embodiment, there can be two or more coils, such as making one coil surround the second permanent magnet as in the described embodiment, but another coil surrounds the first permanent magnet. In addition, it is not required that the coil always surrounds the permanent magnet, although such a device helps to keep the vertical size of the structure small. At least one coil can be placed in the space between the permanent magnets. As another alternative, at least one of the permanent magnets can be annular, with the coil placed inside the ring.

Claims

1. An acoustic transducer is used to convert an electrical signal into mechanical vibration at an acoustic frequency. include: - an upper part and a lower part, - a first permanent magnet in the upper part and a second permanent magnet in the lower part, the first permanent magnet and the second permanent magnet having like poles facing each other in the direction of the axis, - an upper cover in the upper part and a lower cover in the lower part, said upper cover and said lower cover comprising a magnetic material and together defining an enclosure surrounding the first permanent magnet and the second permanent magnet, and at least one coil, the coil being located in the housing and being configured to generate a dynamic magnetic force in the direction of the axis under the influence of a current flowing through the coil, in: - a separation gap between the edges of the upper cover and the lower cover pointing substantially in the direction of the axis, thereby allowing the edges of the lower cover and the upper cover to move relative to each other in the direction of the axis between different positions, the positions differing in the extent to which the edges of the upper cover and the lower cover overlap in a direction perpendicular to the axis, Features: - the upper cover has a U-shaped cross section, and the first permanent magnet is located inside the U-shaped ring, - said lower cover has a plate-shaped cross section, the outer edge of the plate defining said edge of the lower cover, and - the second permanent magnet is located on the side of the plate facing the inside of the U-shaped cross section of the upper cover; The acoustic transducer has a spontaneous tendency to seek equilibrium at a nominal design point, such that if the vertical separation between the upper member and the lower member is smaller than at the nominal design point, the repulsive static magnetic force component prevails and attempts to push the upper member and the lower member further away from each other toward the nominal design point, and if the vertical separation is larger than at the nominal design point, the attractive static magnetic force component prevails and attempts to pull the upper member and the lower member closer together toward the nominal design point.

2. The acoustic transducer according to claim 1, in: a cover with a U-shaped cross section comprising a first cup part having a skirt portion which is closed at one end by an end portion and is open at the other end, - said cover having a U-shaped cross section comprises a gasket member having an outer edge and an inner edge, wherein said inner edge defines an opening smaller than the inner dimensions of said skirt portion, and - said gasket member is attached to the open end of the skirt portion concentrically with said first cup member such that an inner edge of the gasket member defines said rim of the lid having a U-shaped cross section.

3. The acoustic transducer according to claim 1, comprising a support member configured to resist relative movement of the upper and lower members in a direction perpendicular to the axis while allowing relative movement of the upper and lower members in the direction of the axis. 4 . The acoustic transducer according to claim 3 , wherein the supporting member comprises a multi-branched coil spring, a central portion of which is attached to the lower part, and ends of which are attached to the upper part. 5 . The acoustic transducer of claim 3 , wherein the support member comprises a foil attached to the upper and lower members and bridging the separation gap.

6. An acoustic transducer according to claim 5, wherein at least a portion of the foil constitutes a flexible printed circuit for transmitting electrical signals to the at least one coil.

7. An acoustic transducer for converting an electrical signal into mechanical vibration at an acoustic frequency, the acoustic transducer include: - an upper part and a lower part, - a first permanent magnet in the upper part and a second permanent magnet in the lower part, the first permanent magnet and the second permanent magnet having like poles facing each other in the direction of the axis, - an upper cover in the upper part and a lower cover in the lower part, said upper cover and said lower cover comprising a magnetic material and together defining an enclosure surrounding the first permanent magnet and the second permanent magnet, and at least one coil, the coil being located in the housing and being configured to generate a dynamic magnetic force in the direction of the axis under the influence of a current flowing through the coil, in: - a separation gap between the edges of the upper cover and the lower cover pointing substantially in the direction of the axis, thereby allowing the edges of the lower cover and the upper cover to move relative to each other in the direction of the axis between different positions, the positions differing in the extent to which the edges of the upper cover and the lower cover overlap in a direction perpendicular to the axis, Features: - the lower cover has a U-shaped cross section, and the second permanent magnet is located inside the U-shaped ring, - the upper cover has a plate-shaped cross section, the outer edge of the plate defining the edge of the upper cover, and - the first permanent magnet is located on the side of the plate facing the inside of the U-shaped cross section of the lower cover; The acoustic transducer has a spontaneous tendency to seek equilibrium at a nominal design point, such that if the vertical separation between the upper member and the lower member is smaller than at the nominal design point, the repulsive static magnetic force component prevails and attempts to push the upper member and the lower member further away from each other toward the nominal design point, and if the vertical separation is larger than at the nominal design point, the attractive static magnetic force component prevails and attempts to pull the upper member and the lower member closer together toward the nominal design point.

8. The acoustic transducer according to claim 7, comprising a support member configured to resist relative movement of the upper and lower members in a direction perpendicular to the axis while allowing relative movement of the upper and lower members in the direction of the axis. 9 . The acoustic transducer according to claim 8 , wherein the supporting member comprises a multi-branched coil spring, a central portion of which is attached to the upper member, and ends of which are attached to the lower member.

10. The acoustic transducer of claim 8, wherein the support member comprises a foil attached to the upper and lower members and bridging the separation gap.

11. An acoustic transducer according to claim 10, wherein at least a portion of the foil constitutes a flexible printed circuit for transmitting electrical signals to the at least one coil.

12. The acoustic transducer according to any one of claims 1 or 7, in: - In the U-shaped cross section, the ends of the arms of the U-shape comprise inwardly projecting extensions, the inner extremities of the extensions defining the edges of the cover having the U-shaped cross section.

13. The acoustic transducer according to claim 12, wherein - a cover having a U-shaped cross section comprising a first cup part and a second cup part, each cup part having a skirt portion and an end portion, - said second cup part is in an inverted position relative to said first cup part, - the skirt portion of the second cup part is at least partially located inside the skirt portion of the first cup part, and - The end portion of the second cup part has an opening, the edge of which defines the edge of the cover having a U-shaped cross section.

14. The acoustic transducer according to claim 13, in: - the skirt portion of the second cup part is located inside the skirt portion of the first cup part over a majority of the length of the skirt portion of the second cup part, and - The permanent magnet inside the cover having a U-shaped cross section is located inside the skirt portion of the first cup part and the second cup part.

15. The acoustic transducer according to claim 13, in: - the length of the skirt portion of the first cup part is greater than the length of the skirt portion of the second cup part, - a permanent magnet inside the cover having a U-shaped cross section located inside the skirt portion of the first cup part, and - The permanent magnet inside the cover having a U-shaped cross section and the second cup part are stacked inside the skirt portion of the first cup part.

16. The acoustic transducer according to claim 14, in: - A sheet of magnetic material is stacked between said permanent magnet and the end portion of the first cup part inside the cover having a U-shaped cross section.

17. The acoustic transducer according to claim 15, in: - A sheet of magnetic material is stacked between said permanent magnet and the end portion of the first cup part inside the cover having a U-shaped cross section.

18. The acoustic transducer according to claim 12, in: - a cover having a U-shaped cross section comprising a first cup part and a second cup part, each cup part having a skirt portion and an end portion, - said second cup part is oriented in the same way relative to the first cup part and is located inside said first cup part, - the skirt portion of the second cup part comprises a perforated area of ​​the skirt portion at an intermediate longitudinal level of the skirt portion, - the skirt portion of the second cup part comprises, at one end thereof opposite to the end portion, a solid area defining said edge of the lid having a U-shaped cross section.

19. Devices for producing sound, include: - an electronic device having a first structural component and a second structural component, - at least one acoustic transducer according to any one of claims 1 to 18, the upper part of the acoustic transducer being attached to the first structural part and the lower part of the acoustic transducer being attached to the second structural part of the electronic device, and - an electric circuit, as part of the electronic device, configured to feed an electric signal to the at least one coil of the acoustic transducer.

20. The device of claim 19, wherein the first structural member comprises a visible exterior surface of the electronic device.

21. The device of claim 19, wherein the first structural component comprises a display of the electronic device.

22. The device of any one of claims 19 to 21, wherein the second structural member comprises a portion of a structural support frame of an electronic device.

23. The device according to any one of claims 19 to 21, in: - the upper part of the acoustic transducer has a first lateral dimension on the side where the upper part is attached to the first structural part, the device comprises a first non-elastic attachment member between the upper part and the first structural part for transmitting a movement of the upper part in the direction of the axis into the first structural part, and - The first attachment member has a second lateral dimension that is smaller than the first lateral dimension.

24. The device according to claim 23, in: - the device comprises a resilient second attachment member between the upper part and those parts of the first structural part not covered by the first attachment member, the second attachment member being used to stabilize the upper part against tilting relative to the first structural part.

25. The apparatus of claim 24, wherein the second attachment member comprises at least one of a resiliently deformable cushioning material and a spring branch extending on the first structural component further than the first lateral dimension of the upper component.

26. A device according to any one of claims 19 to 21, comprising a support sheet between the upper member and the first structural member for matching the local elastic properties of the first structural member with the movement transmitted to the first structural member by the upper member.

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