METHOD OF MANUFACTURING SOUND-GENERATING APPARATUS

A magnetic-field-generating unit and a coil vibrates an armature. The armature drives a diaphragm. The armature is formed of a rolled metal plate made of Permalloy. A workpiece is cut out of an unannealed metal plate with a wire saw or by etching such that the long-side direction of the workpiece corresponds to a transverse direction that is orthogonal to the direction of rolling performed on the metal plate. The cut-out workpiece is bent and is then annealed. Through this process, the warp of the armature is minimized.

BACKGROUND

1. Field of the Disclosure

The present disclosure relates to a method of manufacturing a sound-generating apparatus configured to vibrate a diaphragm by driving an armature made of a magnetic metal plate.

2. Description of the Related Art

An arrangement relating to a sound-generating apparatus (an acoustic transducer) is disclosed by Japanese Unexamined Patent Application Publication No. 2012-4850.

This sound-generating apparatus includes a holder frame fixedly provided in a case member. The holder frame has an opening. The opening is closed by a resin film. A diaphragm made of a thin metal plate is pasted to the resin film within the opening.

The holder frame is provided with an armature fixed thereto. The armature includes a vibrating portion and a fixed portion that are integrated with each other. The fixed portion is fixed to the holder frame. The armature is provided with a coil and a yoke fixed thereto. The yoke is provided with two magnets fixed thereto.

The vibrating portion forming a part of the armature is positioned in a void provided in the center of winding of the coil and in the gap between the two magnets. The tip of the vibrating portion and the diaphragm are connected to each other with a beam member.

When the armature of the sound-generating apparatus configured as above is magnetized with a voice current supplied to the coil, the vibrating portion vibrates by the effect of the magnetization and the magnetic field produced by the magnets. The vibration is transmitted through the beam member to the diaphragm, and the diaphragm vibrates, whereby a sound is generated.

In the related-art sound-generating apparatus disclosed by Japanese Unexamined Patent Application Publication No. 2012-4850, the armature is formed of a magnetic metal plate. Such a metal plate has an adjusted thickness by being rolled in one axial direction.

The vibrating portion of the armature has an elongated shape. If the armature is obtained by cutting the metal plate such that the long-side direction of the vibrating portion corresponds to the direction of rolling performed on the metal plate, the internal stress having been generated in the metal plate during the rolling is released, whereby the metal plate warps. In such a state, it is difficult to appropriately set the gap between the vibrating portion and each of the magnets.

The magnetic permeability of the magnetic metal material can be increased by annealing. If an armature is cut out of a metal plate after the metal plate is annealed, the internal stress generated after the annealing makes the warp of the cut-out armature greater.

SUMMARY

According to an aspect of the present invention, there is provided a method of manufacturing a sound-generating apparatus including an armature made of a magnetic material and that vibrates in a plate-thickness direction with a base portion of the armature being supported, a drive mechanism that vibrates the armature, and a diaphragm that is vibrated by the armature. The method includes forming the armature into an elongated shape from a rolled magnetic metal plate such that a long-side direction of the armature corresponds to a direction intersecting a direction of rolling performed on the metal plate.

A magnetic material can have higher magnetic permeability by being annealed. Accordingly, if the armature having cut out of a metal plate is annealed, the warp of the armature can further be reduced. Moreover, in the case of an armature including a bent portion, if the armature is annealed after being cut out of the metal plate and being bent, the warp of the armature can further be reduced.

DESCRIPTION OF THE EXAMPLARY EMBODIMENTS

FIGS. 1 to 4illustrate a sound-generating apparatus1according to a first embodiment of the present invention.

The sound-generating apparatus1includes a case2. The case2includes a lower case3and an upper case4. The lower case3and the upper case4are each made of synthetic resin or nonmagnetic metal.

Referring toFIG. 2, the lower case3has a bottom part3a, a sidewall part3bforming the four side faces, and an opening edge3cat the upper end of the sidewall part3b. The upper case4has a top part4a, a sidewall part4bforming the four side faces, and an opening edge4cat the lower end of the sidewall part4b. The space in the lower case3is larger than the space in the upper case4. The upper case4serves as a lid for the lower case3.

Referring toFIG. 3, a driving-side frame5is held between the opening edge3cof the lower case3and the opening edge4cof the upper case4. The lower case3, the upper case4, and the driving-side frame5are fixed to one another with adhesive or the like.

Referring toFIG. 2, the driving-side frame5is a plate having a uniform thickness in the Z direction. The driving-side frame5has a driving-side attaching surface5aon the lower side inFIG. 2and a joining surface5bon the upper side inFIG. 2. The driving-side frame5has a driving-side opening5cprovided in a central part thereof and extending vertically therethrough. The driving-side frame5is a magnetic metal plate made of SUS430 (18-chrome stainless steel), cold-rolled steel such as SPCC, or the like.

A vibrating-side frame6is provided on the upper side of the driving-side frame5inFIG. 2. As illustrated inFIGS. 2 and 4, the vibrating-side frame6has a frame shape having a wide vibrating-side opening6cin a central part thereof. A frame part of the vibrating-side frame6has a uniform thickness in the Z direction and has a vibrating-side attaching surface6aon the upper side thereof and a joining surface6bon the lower side thereof in the drawings. The vibrating-side frame6is a nonmagnetic metal plate made of SUS304 (18-chrome 8-nickel stainless steel: 18-8 stainless steel) or the like.

Referring toFIG. 3, the vibrating-side frame6is provided on the driving-side frame5, and the joining surface5bof the driving-side frame5and the joining surface6bof the vibrating-side frame6are joined to each other by surface joining. The driving-side frame5and the vibrating-side frame6are positioned relative to each other and are fixed to each other in that state by laser welding or with adhesive.

Referring toFIGS. 2 and 3, the vibrating-side frame6is provided with a diaphragm11and a flexible sheet12. The diaphragm11is made of a thin metal material such as aluminum or SUS304 and has ribs according to need. The ribs are formed by pressing so that the bending strength of the diaphragm11is increased. The flexible sheet12is easier to bend and deform than the diaphragm11. The flexible sheet12is a resin sheet (a resin film) made of polyethylene terephthalate (PET), nylon, polyester, or the like.

The diaphragm11is bonded to the lower surface of the flexible sheet12and is thus fixed. An outer peripheral edge12a(seeFIG. 2) of the flexible sheet12is fixed to the vibrating-side attaching surface6a, i.e., the upper surface of the frame part of the vibrating-side frame6, with adhesive. Hence, the diaphragm11is supported by the vibrating-side frame6with the aid of the flexible sheet12and in a vibratable state.

The diaphragm11has a free end11band a fulcrum end11c, which are the ends in the Y direction. The diaphragm11is vibratable, with the fulcrum end11cserving as the fulcrum, such that the free end11bis displaced in the Z direction.

Referring toFIGS. 2, 3, and 4, the driving-side frame5is provided with a magnetic-field-generating unit20. The magnetic-field-generating unit20is an assembly including an upper yoke21, a lower yoke22, and a pair of side yokes23. The upper yoke21, the lower yoke22, and the side yokes23are each made of a magnetic metal material, for example, cold-rolled steel plate such as SPCC, or a magnetic metal plate of SUS430 (18-chrome stainless steel).

Referring toFIG. 4, the upper yoke21and the lower yoke22each have a flat shape and face each other with a gap interposed therebetween in the Z direction. A surface of the upper yoke21that faces upward inFIG. 4serves as a joining surface21ato be joined to the driving-side frame5. A surface of the upper yoke21that faces downward, or inward, inFIG. 4serves as a counter surface21b. A surface of the lower yoke22that faces upward, or inward, inFIG. 4serves as a counter surface22b.

The side yokes23each have a flat shape with the same thickness as the upper yoke21and the lower yoke22. A surface of each of the side yokes23that faces the other of the side yokes23serves as a side counter surface23a. The side counter surfaces23aof the respective side yokes23are parallel to each other and are each perpendicular to the counter surfaces21band22bof the upper yoke21and the lower yoke22. The side yokes23face each other with a gap interposed therebetween in the X direction.

Upper end faces23bof the respective side yokes23are in contact with the counter surface21bof the upper yoke21and are fixed thereto by laser welding or bonding. Lower end faces23cof the respective side yokes23are in contact with the counter surface22bof the lower yoke22and are fixed thereto by laser welding or bonding.

In the magnetic-field-generating unit20, an upper magnet24is fixed to the counter surface21bof the upper yoke21, and a lower magnet25is fixed to the counter surface22bof the lower yoke22. A lower surface24aof the upper magnet24and an upper surface25aof the lower magnet25A face each other with a gap δ in the Z direction interposed therebetween. The magnets24and25are magnetized such that the lower surface24aof the upper magnet24and the upper surface25aof the lower magnet25have opposite polarity with respect to each other.

The joining surface21a, i.e., the upper surface, of the upper yoke21is flat. As illustrated inFIG. 4and others, the joining surface21ais joined to the driving-side attaching surface5a, i.e., the lower surface, of the driving-side frame5by surface joining and is fixed thereto by laser welding or with adhesive.

Referring toFIGS. 2 and 3, a coil27is provided next to the magnetic-field-generating unit20. The coil27includes a conducting wire wound around a winding-center line extending in the Y direction. A vibrating portion32aof an armature32is positioned in a space27cprovided in the center of winding of the coil27. The conducting wire of the coil27is wound in such a manner as to encircle the armature32.

An end face of the coil27that faces toward the left side in the Y direction serves as a joining surface27a. The joining surface27ais fixed to the upper yoke21and the lower yoke22of the magnetic-field-generating unit20with respective adhesive layers28interposed therebetween. In fixing the joining surface27ato the magnetic-field-generating unit20, the coil27and the magnetic-field-generating unit20are positioned such that the winding-center line of the coil27coincides with the center of the6between the upper magnet24and the lower magnet25.

In the first embodiment, the magnetic-field-generating unit20and the coil27form a drive mechanism that vibrates the armature32.

Referring toFIG. 3, a supporting member31is fixed to the driving-side attaching surface5a, i.e., the lower surface, of the driving-side frame5. The supporting member31has an upper surface31a, a lower surface31b, and a rear end surface31c. The upper surface31aand the lower surface31bare flat surfaces that are parallel to each other. The rear end surface31cis perpendicular to the upper surface31a. The upper surface31aof the supporting member31is joined to the driving-side attaching surface5aby surface joining and is fixed thereto by laser welding or the like.

The armature32is attached to the lower surface31bof the supporting member31. The armature32and the supporting member31are each made of a magnetic material. The supporting member31is made of cold-rolled steel such as SPCC or SUS430 (18-chrome stainless steel). The armature32is made of a Ni—Fe alloy (Permalloy), which is a magnetic material.

Referring toFIG. 3, the armature32includes the vibrating portion32a, a base portion32bextending substantially perpendicularly from the vibrating portion32a, and a tip portion32c. The tip portion32chas a recess32dat the widthwise center thereof.

The base portion32bof the armature32is joined to the rear end surface31cof the supporting member31by surface joining and is fixed thereto by laser welding or the like. As illustrated inFIG. 3, the vibrating portion32ais positioned in the space27cprovided in the center of winding of the coil27and in the gap δ between the upper magnet24and the lower magnet25. The tip portion32cof the armature32projects from the gap δ frontward in the Y direction.

As illustrated inFIG. 3, the free end11bof the diaphragm11and the tip portion32cof the armature32are connected to each other with a transmitting member33. The transmitting member33is a needle-like member made of metal or synthetic resin. A fixed portion33aof the transmitting member33that is at the upper end is fixed to the diaphragm11. A connecting end33bof the transmitting member33that is at the lower end extends through the recess32dof the armature32. The connecting end33band the armature32are fixed to each other with adhesive.

The armature32is a plate made of a Ni—Fe alloy (Permalloy). The plate has been rolled in one axial direction between rollers so that the thickness thereof is made uniform. Hereinafter, the direction in which the plate is rolled is referred to as “machining direction” and is abbreviated to MD, and a direction orthogonal to the MD is referred to as “transverse direction” and is abbreviated to TD. The armature32has an elongated shape with the length thereof in the Y direction being generally greater than the width thereof in the X direction. The long-side direction (the Y direction) of the armature32corresponds to the TD.

A rolled metal plate has an internal stress accumulated in the rolling process. Therefore, when such a metal plate is cut into pieces each having the size of the armature32, the internal stress is released, whereby the plate warps. The warp occurs greater in the MD than in the TD. Hence, if the plate is machined for outlining the armature32such that the TD corresponds to the long-side direction of the armature32, the warp of the resulting armature32in the long-side direction that tends to occur immediately after the machining of the plate can be reduced.

A magnetic metal material such as Permalloy can have increased magnetic permeability by being annealed. However, if a large rolled plate is annealed first, the internal stress generated therein further increases. Accordingly, if such a large rolled plate is cut into pieces of armatures32after being annealed, the internal stress generated in the annealing is also released. Consequently, the warp becomes greater. Hence, to obtain the armature32, it is preferable to first cut a plate into pieces of armatures32such that the long-side direction of each armature32corresponds to the TD, to then bend the armature32in such a manner as to form a base portion32b, and to then anneal the bent armature32. If a flat armature32that does not need to be bent to form the base portion32bis employed, it is preferable to first cut a plate into pieces of armatures32such that the long-side direction of each armature32corresponds to the TD, and to then anneal the armature32.

If a rolled metal plate is cut into pieces of elongated but small armatures32and the armatures32are then annealed, the accumulation of internal stress during the annealing can be reduced. Accordingly, such armatures32have substantially no warp caused by annealing.

In the outline machining of a rolled plate for obtaining armatures32, it is preferable to employ a cutting method that causes less damage during the machining. For example, it is preferable to machine the outline of each armature32by using a wire saw or by etching. If armatures32are machined out of a plate with a wire saw or by etching, the increase in the warp that may be caused by outline machining can be suppressed.

An armature32obtained by outline machining of a plate such that the long-side direction thereof corresponds to the TD and that is annealed after the outline machining can have a reduced warp in the long-side direction (the Y direction) of the vibrating portion32athereof. Hence, when the armature32is assembled with other elements, the tip portion32cthereof can be easily positioned at the center of the gap δ between the upper magnet24and the lower magnet25. Therefore, the assembling work and the adjustment work are facilitated, and a sound-generating apparatus1with high dimensional accuracy can be obtained.

Referring toFIG. 3, since the lower case3and the upper case4are fixed to each other with the driving-side frame5interposed therebetween, the space in the case2is divided into upper and lower spaces by the diaphragm11and the flexible sheet12. The space above the diaphragm11and the flexible sheet12and in the upper case4serves as a sound-generating space. The sound-generating space communicates with the outside through a sound-generating port4dprovided in the sidewall part4bof the upper case4. The bottom part3aof the lower case3has an exhaust port3d, through which the space below the diaphragm11and the flexible sheet12and in the lower case3communicates with the outside.

The sidewall part3bof the lower case3has a wiring hole3ethrough which a wiring line that conducts electricity to the coil27is drawn to the outside.

Now, the operation of the sound-generating apparatus1will be described.

When a voice current is supplied to the coil27, the armature32is induced to produce a magnetic field. The magnetic field produced by the armature32and the magnetic field produced in the gap δ between the upper magnet24and the lower magnet25cause the vibrating portion32aof the armature32to vibrate in the Z direction. The vibration is transmitted through the transmitting member33to the diaphragm11, whereby the diaphragm11vibrates. Specifically, the diaphragm11supported by the flexible sheet12vibrates such that the free end11bthereof vibrates in the Z direction with the fulcrum end11cthereof serving as the fulcrum. The vibration of the diaphragm11generates a sound pressure in the sound-generating space of the upper case4, and the sound pressure is outputted to the outside through the sound-generating port4d.

FIG. 5illustrates a sound-generating apparatus101according to a second embodiment of the present invention.

The sound-generating apparatus101has the same configuration as the sound-generating apparatus1according to the first embodiment, except the configuration of the armature.

An armature132employed in the sound-generating apparatus101includes a vibrating portion132a, a folded U portion132bat the base end of the vibrating portion132a, and a fixed portion132econtinuous with the folded U portion132b. The vibrating portion132a, the folded U portion132b, and the fixed portion132eare integrated with one another. The armature132is folded such that the fixed portion132eextends parallel to the vibrating portion132a. A tip portion132cof the armature132has a recess132d.

The sound-generating apparatus101does not include the supporting member31. The fixed portion132eof the armature132is directly fixed to the driving-side attaching surface5aof the driving-side frame5. The armature132is elastically deformable from a boundary132fbetween the folded U portion132band the fixed portion132eto the tip portion132c. Therefore, the armature132is vibratable with a large displacement. Accordingly, the diaphragm11can have a large amplitude, whereby the sound to be outputted is increased.

The armature132of the sound-generating apparatus101illustrated inFIG. 5is also obtained by cutting a Permalloy plate with a wire saw or by etching such that the long-side direction of the armature132corresponds to the TD (the Y direction). Then, the armature132is folded at the base portion to form the folded U portion132band the fixed portion132e, and is annealed.

Examples

Table 1 below summarizes the results of measurement of warps occurred in a pressed workpiece and Workpieces 1 to 8.

The pressed workpiece listed in Table 1 is a basic example for comparison with examples according to the present invention and was obtained through a pressing process in which a workpiece having a width of 1 mm and a length of 5.5 mm was machined out of a rolled metal plate made of Permalloy and having a thickness of 0.15 mm. The long-side direction of the workpiece corresponded to the MD. This workpiece was bent perpendicularly to form a base portion32bas illustrated inFIG. 3, whereby the workpiece was obtained as an armature. Subsequently, the workpiece was annealed by being heated to 1100° C. in a hydrogen atmosphere.

Table 1 summarizes measured values defining a warp occurred in the vibrating portion of the pressed workpiece (armature) obtained as above. The warp was measured with a laser displacement meter.FIG. 8is a graph of measured displacements from a center line extending in the Y direction for a plurality of workpieces each prepared as the pressed workpiece. As can be seen from Table 1, the average displacement on the positive side was 5.6 μm, the average displacement on the negative side was 5.6 μm, and the average warp width was 11.2 μm. The average warp width of 11.2 μm is plotted for the pressed workpiece in the graph illustrated inFIG. 6.

Workpieces 1 to 8 listed in Table 1 were each obtained by cutting a rolled metal plate made of Permalloy and having a thickness of 0.15 mm into pieces each having a width of 1 mm and a length of 5.5 mm by a cutting method that causes less damage. In the cutting process, the outlines of Workpieces 1 to 4 were machined with a wire saw, and the outlines of Workpieces 5 to 8 were machined by etching.

Workpiece 1 was not annealed before the outline thereof was machined with the wire saw. The long-side direction of Workpiece 1 corresponded to the MD. Workpiece 2 was not annealed before the outline thereof was machined with the wire saw. The long-side direction of Workpiece 2 corresponded to the TD. Workpiece 3 was annealed before the outline thereof was machined with the wire saw. In the annealing process, Workpiece 3 was heated to 1100° C. in a hydrogen atmosphere. The long-side direction of Workpiece 3 corresponded to the MD. Workpiece 4 was annealed before the outline thereof was machined with the wire saw. The long-side direction of Workpiece 4 corresponded to the TD.

Workpiece 5 was not annealed before the outline thereof was machined by etching. The long-side direction of Workpiece 5 corresponded to the MD. Workpiece 6 was not annealed before the outline thereof was machined by etching. The long-side direction of Workpiece 6 corresponded to the TD. Workpiece 7 was annealed before the outline thereof was machined by etching. In the annealing process, Workpiece 7 was heated to 1100° C. in a hydrogen atmosphere. The long-side direction of Workpiece 7 corresponded to the MD. Workpiece 8 was annealed before the outline thereof was machined by etching. The long-side direction of Workpiece 8 corresponded to the TD.

FIGS. 10A and 10Bare each an enlarged photograph of a plate surface for reference.FIG. 10Ashows the surface of Workpiece 6, that is, the surface of a workpiece that was machined out by etching without being annealed and whose long-side direction corresponded to the TD.FIG. 10Bshows the surface of Workpiece 8, that is, the surface of a workpiece that was machined out by etching after being annealed and whose long-side direction corresponded to the TD.

The average warp widths of Workpieces 1 to 8 summarized in Table 1 are plotted in the graph illustrated inFIG. 6, along with the average warp width of the pressed workpiece.

As can be seen from Table 1 andFIG. 6, among the workpieces that were machined out with the wire saw, Workpiece 2 obtained without being annealed before being machined out and whose long-side direction corresponded to the TD had the smallest warp. Likewise, among the workpieces that were machined out by etching, Workpiece 6 obtained without being annealed before being machined out and whose long-side direction corresponded to the TD had the smallest warp.

The magnetic metal plate after being rolled has a residual stress thereinside. If a workpiece of size 1 mm by 5.5 mm, for example, is machined out of such a magnetic metal plate, the internal stress is released, and the workpiece is therefore likely to warp. Such a warp tends to be greater in the MD. Therefore, orienting the workpiece such that the long-side direction thereof corresponds to the TD can reduce the size of the warp. On the other hand, the magnetic permeability of a magnetic metal plate is improved by annealing. However, if a plate having a large area is annealed, the internal stress that remains in the plate also becomes large. Therefore, it is preferable not to anneal the plate before a workpiece is machined out.

Table 2 below summarizes the average warp widths of a plurality of samples measured as Workpiece 2, that is, samples that were machined out with the wire saw without being annealed and such that the long-side direction thereof corresponded to the TD. The samples include those for “Step 1” that were subjected to measurement immediately after the outline machining, those for “Step 2” that were subjected to measurement after the machined workpieces were each bent substantially perpendicularly at a base portion as illustrated inFIG. 3, and those for “Step 3” that were subjected to measurement after the bending and the annealing.

Table 2 also summarizes the average warp widths of a plurality of samples measured as Workpiece 4, that is, samples that were machined out with the wire saw after being annealed and such that the long-side direction thereof corresponded to the TD. The samples include those for “Step A” that were subjected to measurement immediately after the outline machining, and those for “Step B” that were subjected to measurement after the machined workpiece is bent substantially perpendicularly at a base portion as illustrated inFIG. 3.

FIG. 9is a graph of displacements of a plurality of armatures obtained after “Step 3” that were measured with reference to the center line extending in the Y direction and with a laser displacement meter.

As summarized for Step 3, it is found to be preferable to employ an armature obtained by machining a workpiece out of an unannealed metal plate and then annealing the workpiece after bending the workpiece. Even if an armature including no bent portion is employed, the armature is preferably machine out of an unannealed metal plate.