JPH09331596A - Thin profile electromagnetic transducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a large amplitude by suppressing production of abnormal tone (noise) due to resonance of a diaphragm at its circumferential part so as to attain free vibration of the diaphragm locally and entirely, to attain ease of manufacture of the transducer and ease of thin profile. SOLUTION: The transducer is provided with a permanent magnet board 10, a diaphragm 12 opposite thereto, a cushion member 14 interposed between them, and a support member 16 to restrict the position of the diaphragm 12 with respect to the permanent magnet board 10. The permanent magnet board 10 has multi-pole magnetizing patterns in parallel stripes and has an integral structure where exhaust throughholes 18 are arranged to a neutral zone. The diaphragm 12 is structured so that a coil 22 is print-wired to a thin and flexible resin film 20, a straight line part of the coil 22 is provided to a position corresponding to the neutral zone of the permanent magnet board 10 and the diaphragm 12 is supported so as to be freely displaced in the broadwise direction entirely. A buffer member 14 is so structured that a plurality of soft and porous sheets whose size is nearly equal to the size of the diaphragm 12 are stacked.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin-type electromagnetic converter, and more specifically, it will be described in more detail. The present invention relates to a thin electromagnetic converter having a vibrating film having a meandering coil pattern and a buffer member interposed between the permanent magnet and the vibrating film. This thin electromagnetic converter is useful for, for example, a flat panel speaker, headphones, or a microphone.

[0002]

2. Description of the Related Art An electromagnetic transducer having a flat plate structure in which a permanent magnet and a vibrating membrane are combined has been known. This type of electromagnetic converter usually includes a permanent magnet structure, a vibrating membrane arranged so as to face the permanent magnet, and a support member for fixing the vibrating membrane to the permanent magnet structure at a peripheral portion. are doing.

Here, the conventional permanent magnet structure used in this type of electromagnetic converter is composed of a large number of rod-shaped permanent magnets that are magnetized on both sides with two poles (magnetization in the vertical direction of the structure). The magnetic poles are arranged in parallel and alternately so that the magnetic poles are different from each other, and the magnetic poles are coupled and fixed to each other by a non-magnetic structural member. As the vibrating film, a thin resin film having a coil formed of a meandering conductive wire pattern formed on the surface or inside thereof is used. Then, the vibrating film is combined with the permanent magnet structure in such a positional relationship that the straight line portion of the meandering conductive wire pattern corresponds to the middle portion between the rod-shaped permanent magnets arranged in parallel. Actually, the structure is such that it is fixed to the permanent magnet structure via a spacer at the periphery of the vibrating film.

Magnetic lines of force pass between the magnetic poles of adjacent rod-shaped permanent magnets, and a magnetic field is generated that crosses the straight line portion of the conductor pattern of the vibrating membrane. Then, when the coil of the vibrating membrane is energized,
An electromagnetic force according to Fleming's left-hand rule is generated, and the vibrating membrane is displaced in the thickness direction. According to this principle, vibration corresponding to the drive current to the coil is generated and a sound wave is generated. The sound wave is radiated to the outside through the space between the rod-shaped permanent magnets.

[0005]

In order to improve the performance of the conventional permanent magnet structure, it is desirable to arrange the elongated rod-shaped permanent magnets as densely as possible. However, for example, if the permanent magnet used is a sintered magnet (ferrite magnet), the more elongated the shape, the more difficult it is to manufacture with high accuracy (deformation such as warpage occurs during firing). It becomes difficult to provide sufficient mechanical strength. Further, since a large magnetic force acts between the rod-shaped permanent magnets, it is extremely difficult to assemble the elongated rod-shaped permanent magnets close to each other and to assemble them accurately. In addition, since the rod-shaped permanent magnets are separated from each other, magnetic poles appear not only on both sides in the thickness direction but also on the edge portions between the upper and lower surfaces and the side surfaces, and part of the side surfaces, so that horizontal magnetism between adjacent rod-shaped permanent magnets is increased. There is also a problem that the magnetic flux will fly in the direction (linearly in the gap), the number of magnetic force lines interlinking with the coil of the vibrating membrane (the straight line portion of the conductor pattern) will decrease, and the drive efficiency will deteriorate. .

As a result, many rod-shaped permanent magnets are
There is no choice but to dispose them at a wide distance from each other, which makes it necessary to widen the distance between the permanent magnet structure and the vibrating membrane.
In that respect as well, the conversion efficiency becomes poor and the entire electromagnetic converter becomes thick.

Further, in the prior art, since the structure in which the vibrating membrane is firmly pressed by the spacer at the peripheral portion is adopted, a fulcrum is generated at the peripheral portion, resulting in a so-called "sticky" vibration, resulting in a drive current. There is a problem in that it is difficult to produce a reproduced sound that is faithful to, and the amplitude cannot be increased.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide an electromagnetic converter which is easy to manufacture and thin. Another object of the present invention is to suppress the generation of abnormal noise (noise) due to resonance in the peripheral portion of the vibrating film, and to allow the vibrating film to freely vibrate locally or entirely,
It is an object of the present invention to provide a thin electromagnetic converter which is devised so that a large vibration amplitude can be obtained and at the same time outputs a sound faithful to a drive current.

[0009]

SUMMARY OF THE INVENTION The present invention comprises a permanent magnet plate and a vibrating membrane arranged so as to face the permanent magnet plate.
A thin electromagnetic converter comprising a cushioning member interposed between the vibrating membrane and the permanent magnet plate, and a supporting member for regulating a relative position of the vibrating membrane with respect to the permanent magnet plate. The permanent magnet plate has a strip-shaped N
A parallel striped multi-pole magnetized pattern in which poles and S poles alternately appear is formed, and a large number of exhaust through holes are arranged at the neutral zone position in the magnetized pattern to form an integrated structure. The vibrating film has a structure in which a coil made of a meandering (reciprocating) conductive wire pattern is printed on a thin and flexible resin film, and the linear part of the conductive wire pattern corresponds to the neutral zone of the permanent magnet plate. The support member is provided so that it is not fixed in the peripheral portion and its displacement in the in-plane direction is restricted by the support member, but it is supported so as to be freely displaced in the thickness direction. Further, the buffer member has a structure in which a plurality of sheets that are soft and breathable and have substantially the same size as the vibration film are stacked, and that there is a gap between the sheet and the permanent magnet plate or the vibration film. It is arranged as follows.

The permanent magnet plate and the buffer member may be arranged only on one side of the vibrating membrane, but they are arranged on both sides of the vibrating membrane so as to sandwich the vibrating membrane, and both permanent magnet plates are respectively arranged. It is desirable that the neutral zones of No. 1 are aligned and the same poles are opposed to each other with a positional relationship such that they are fixed at intervals. In that case, the structure does not necessarily have to be symmetrical with respect to the vibrating membrane. Therefore, both permanent magnet plates are
The same material and the same shape may be used, or different materials and different shapes (thicknesses) may be used. The permanent magnet plate may be, for example, a sintered magnet, a plastic magnet or a metal magnet.

The meandering (reciprocating) conductive wire pattern serving as a coil may be formed on only one side of the resin film,
You may form on both surfaces. Further, one conductor pattern may be formed corresponding to the center line of each neutral zone of the permanent magnet plate, or a plurality of conductor patterns may be provided. When arranging a plurality of conducting wire patterns in parallel in one neutral zone, it is necessary to distribute them so as to be completely symmetrical with respect to the center line. In any case, it is necessary to maintain the parallel positional relationship between the center line and the conductor pattern.

It is preferable that a high-permeability magnetic plate (for example, an iron plate or a nickel-iron alloy plate) for preventing magnetic flux leakage is closely attached to the surface of the permanent magnet plate opposite to the surface facing the vibrating film. In that case, it is necessary to form a similar exhaust through hole at the same position as the exhaust through hole formed in the permanent magnet plate so that the sound wave generated inside is smoothly radiated to the outside.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION As a result of magnetization, strip-shaped N poles and S poles alternately appear in parallel stripes on the surface of a permanent magnet plate.
The magnetic field component (absolute value) perpendicular to the surface of the permanent magnet plate is the largest near the N pole and the S pole, and the smallest near the boundary between the N pole and the S pole. This is because the component of the magnetizing magnetic field is defined by looking in the vertical direction. Since there is no magnetic field of the vertical component near the boundary between the N pole and the S pole, this region is called the neutral zone. On the other hand, when looking at the horizontal component of the magnetic field (component parallel to the surface of the permanent magnet plate), it is smallest near the N and S poles and largest near the boundary between the N and S poles (neutral zone). This means
It is also clear from the fact that the magnetic force lines pass from the adjacent N pole to the S pole in an arc shape. The magnetic field component that contributes to vibrating the vibrating film in the thickness direction is not the vertical component but the horizontal component (Fleming's left-hand rule). The horizontal component of this magnetic field works most effectively not in the vicinity of each pole but in the position of the neutral zone as described above. Therefore, when the straight line portion of the conductive wire pattern is provided at the position corresponding to the neutral zone, the magnetic force lines pass in a direction crossing the straight line portion of the conductive wire pattern in the plane of the vibrating membrane. Therefore, in such a configuration, the coil (conductor pattern)
When a drive current is supplied to the electromagnetic field, the electromagnetic force is most efficiently generated by the interaction between the current and the magnetic field, and the vibrating film vibrates in the thickness direction. The sound waves generated thereby are emitted to the outside through the exhaust through hole formed in the permanent magnet plate (and the high magnetic permeability magnetic plate). This is the sound generation principle of the electromagnetic converter according to the present invention, and the principle of this electromagnetic conversion is the same as that of the conventional electromagnetic converter of this type.

One of the features of the present invention is that a parallel striped multipole magnetized pattern is formed on almost the entire surface, and a large number of exhaust through holes are arranged at the neutral zone positions in the magnetized pattern. The point is to use a permanent magnet plate having an integrally continuous structure (a structure that is not a combination of individual magnets) as a magnetic drive source. Another feature of the present invention is that the vibrating membrane is not fixed at the peripheral portion but is supported so as to be freely displaced only in the thickness direction. Still another feature of the present invention is that a cushioning member having a structure in which a plurality of soft and breathable sheets are stacked is provided so as to have a gap between the sheet and the permanent magnet plate or the vibrating membrane.

Whether the permanent magnet plate is a sintered magnet or a non-sintered magnet, a flexible magnet or a solid structure magnet, or a material (ferrite magnet, rare earth magnet, neodymium-iron-boron magnet) Etc.), characteristics, etc., and thickness and shape (square, rectangle, circle, ellipse, etc.), structure (whether it is a single permanent magnet plate or a structure in which multiple permanent magnet plates are laminated together). Is optional,
It is a design problem and is appropriately selected according to the characteristics, cost, manufacturing need, usage condition, and the like. Further, the size of the magnetic pole (size of magnetization), the pole pitch, etc. are also arbitrary. There is a configuration in which the permanent magnet plates are arranged only on one side of the vibrating membrane, or there is a configuration in which they are arranged on both sides. Conversely, there is also a configuration in which vibrating membranes are arranged on both sides of the permanent magnet plate so as to sandwich the permanent magnet plate. The conductive wire pattern may be provided on one side of the resin film of the vibrating membrane or may be provided on both sides. The vibrating membrane may be composed of a plurality of resin films. The conductor patterns are arranged so as to correspond to the neutral zones of the permanent magnet plate, but one conductor pattern may be disposed in each neutral zone (one turn configuration), or a plurality of conductor patterns may be disposed (multiple turn configuration). .

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view showing an embodiment of a flat panel speaker which is a kind of thin electromagnetic converter according to the present invention. In the figure, A shows the overall configuration, and B shows an enlarged main part (however, the cushioning member is not shown). This flat speaker includes a permanent magnet plate 10, a vibrating membrane 12 arranged to face the permanent magnet plate 10, a cushioning member 14 interposed between the vibrating membrane 12 and the permanent magnet plate 10, A supporting member 16 for restricting the position of the vibrating membrane 12 with respect to the permanent magnet plate 10 is provided. The permanent magnet plate 10 and the buffer member 14 are symmetrically arranged on both sides of the vibrating membrane 12 so that the same kind of material sandwiches the vibrating membrane 12.

As shown in FIG. 2, the permanent magnet plate 10 is, for example, a square flat plate and is made of a sintered ferrite magnet, and a strip-shaped N pole and an S pole are formed on almost the entire surface of the vibrating film facing surface.
A parallel striped multi-pole magnetized pattern such that poles appear alternately and a neutral zone nz of the magnetized pattern
A large number of exhaust through-holes 18 are arranged at the above position to form an integral structure. The exhaust through holes 18 are formed at a constant pitch along the neutral zone nz, and are arranged in a staggered pattern with a half pitch offset from the exhaust through holes 18 in the adjacent neutral zones nz. They may be arranged in a square lattice pattern so that they are located at the same position in adjacent neutral zones, but if the magnetizing pitch becomes smaller, the hole spacing becomes narrower, which may lower the mechanical strength of the permanent magnet plate and cause cracking. The zigzag pattern as described above is preferable. The shape of the exhaust through-hole 18 may be circular or oval, but an appropriate size and shape are selected and precisely arranged.
This is because if it is too small, the sound waves generated inside are not sufficiently emitted to the outside, and if it is too large, the volume of the permanent magnet plate 10 decreases, the working magnetic field weakens, and the mechanical strength also decreases.

Such a permanent magnet plate 10 can be easily manufactured, for example, by laminating and sintering unsintered multi-hole magnet sheets and sintering them. For multi-pole magnetization, use a magnetizing jig with a structure in which electric wires are embedded in each groove of a magnetizing yoke in which a number of thin grooves are engraved in parallel, and the magnetizing jig and the permanent magnet plate are in close contact with each other. Then, by supplying the pulse current, it is possible to form a parallel striped multi-pole magnetized pattern in which magnetic poles appear in strips on the surface of the permanent magnet plate. In this case, the portion facing the narrow groove becomes the neutral zone.

As shown in FIG. 2, the vibrating membrane 12 is, for example, a biaxially stretched polyethylene terephthalate film (trade name: Mylar) having a thickness of about 30 μm or less.
Alternatively, it is a structure in which a coil 22 having a meandering conductor wire pattern is printed on a thin and flexible resin film 20 such as an aromatic polyimide film (trade name: Kapton). The coil 22 has a linear portion at a position corresponding to the neutral zone nz of the permanent magnet plate 10.
It is provided in parallel with the neutral zone, and is not completely fixed at the peripheral portion, and its displacement in the in-plane direction is restricted by the support member 16, but it is supported so as to be freely displaced in the thickness direction.

Returning to FIG. 1, the cushioning member 14 is soft and breathable (sound waves can freely pass therethrough).
A structure is adopted in which a plurality of sheets 24 having substantially the same size as the vibrating membrane 12 are stacked, and the sheets 24 and the permanent magnet plate 10 are formed.
Alternatively, it is provided so as to have an appropriate gap with the vibrating membrane 12. As the sheet 24, for example, a thin non-woven fabric is preferable, and about 3 sheets (2 to 5 sheets) are provided in a stacked state. Here, the “overlapped state” does not mean that the layers are adhered to each other but simply overlapped in a sparse state so that they can vibrate (displace) separately.
The thickness and material of the non-woven fabric, and the number of sheets to be stacked vary depending on design conditions. The cushioning member 14 is used for the vibration film 12 during operation.
Other than sound waves that are faithful to the sound source, such as preventing the sound from hitting the permanent magnet plate 10 and generating abnormal noise (noise that is not normal vibration sound), and preventing the division vibration of the vibrating membrane itself (preventing chatter noise). Is responsible for appropriately controlling the occurrence of FIG. 1
In No. A, the cushioning member 14 made of a non-woven fabric is drawn by a broken line, but as described above, it is a stack of sheets having substantially the same size as the vibrating membrane.

Both permanent magnet plates 10 are held by a support member 16. Here, the support member 16 is composed of a combination of support rods 26 provided at four corners and nuts 28 screwed at both ends thereof. The two permanent magnet plates 10 are firmly mechanically fixed by the support members 16 so as to maintain a constant positional relationship with each other. Vibrating membrane 1 located between
2 has holes 13 (see FIG. 2) at the four corners, and the holes 13
Although the vibrating membrane 12 is restricted in position in the in-plane direction by inserting the support rod 26 into the, and fitting with a precision of the order of microns, it can be freely displaced in the thickness direction. If the vibrating membrane 12 is displaced in the lateral direction and deviates from the magnetization pattern of the permanent magnet plate 10, it becomes difficult to efficiently generate a sound wave. Therefore, the linear coil portion is supported so as not to come off from the neutral zone. The non-woven fabric, which is a cushioning member, may also have a structure in which holes are provided at the corners and the support rods 26 are inserted and supported. In any case, similarly to the vibrating membrane, it is necessary to be able to freely displace in the thickness direction.

Further, in this embodiment, a high-permeability magnetic plate 30 for preventing magnetic flux leakage is closely attached to the surface of the permanent magnet plate 10 opposite to the surface facing the vibrating film, and the high-permeability magnetic plate 30 is also a permanent magnet. Exhaust through holes 32 similar to the exhaust through holes 18 formed in the plate 10 are formed at the same position so as to communicate with each other. As the high-permeability magnetic plate 30, for example, an iron plate or a nickel-iron alloy (permalloy) plate is suitable.

In the above-described structure, strip-shaped N poles and S poles alternately appear on the surface of the permanent magnet plate 10 (the surface facing the vibrating film) to form a parallel striped magnetization pattern. Since the linear portion of the coil 22 of the vibrating membrane 12 is provided at a position corresponding to the neutral zone (the boundary line between the N pole and the S pole), the linear portion of the coil 22 should be crossed within the plane of the vibrating membrane 12. The magnetic force lines pass in any direction (examples of the magnetic force lines are indicated by arrows in B of FIG. 1). Therefore, when a drive current is supplied to the coil 22, an electromagnetic force is generated in the thickness direction by the interaction between the current and the magnetic field, and the vibrating membrane 12 vibrates.
The sound waves generated by this vibration are exhaust holes 18, 32 formed in the permanent magnet plate 10 and the high-permeability magnetic plate 30.
Will be released to the outside through.

In the electromagnetic converter according to the present invention, it is considered that the sound wave is generated locally from the vibrating membrane 12 (a minute area of the linear portion of the coil 22). That is, the vibrating membrane 12 is
In the peripheral part (edge part), it is not completely fixed,
Since it is in a free state in which it can be displaced in the thickness direction, when a driving current flows through the coil 22, the vibrating membrane 1 is generated by an electromagnetic force according to Fleming's left-hand rule at that portion.
2 will locally vibrate freely. The synthesized vibration, which is a combination of these local vibrations, reaches the ear of the listener and is recognized as sound. Supporting the peripheral part in a free state prevents such local vibrations from being disturbed even in the vicinity of the peripheral part, performs faithful acoustic conversion, and enhances the sound wave generation efficiency of the entire device. This is because.

In the permanent magnet plate 10, lines of magnetic force are generated from an arbitrary N pole on the surface to the adjacent S pole. As described above, the vertical component of the magnetic field is the largest near the N pole and the S pole, but is the smallest near the boundary between the N pole and the S pole. On the other hand, the horizontal component of the magnetic field is smallest near the N and S poles and largest near the boundary between the N and S poles. In the case of one permanent magnet plate, the lines of magnetic force are generated in substantially concentric circles. However, in the case of the above-mentioned embodiment in which two permanent magnet plates are arranged to face each other, the same poles of both permanent magnet plates face each other (N pole and N pole face each other, and S pole and S pole face each other). Therefore, as shown in FIG. 1B, the line of magnetic force from the N pole of one permanent magnet plate to the S pole and the N of the other permanent magnet plate are
The magnetic lines of force from the poles toward the S poles are pressed against each other and are balanced in the central portion to be deformed so that the horizontal component (direction passing through the plane of the vibrating membrane 12) increases. Since the component in the horizontal direction contributes to the generation of sound waves, such a disposition of the permanent magnet plates facing each other particularly when the coil has a plurality of turns (when a plurality of conductor patterns are passed through one neutral zone). In addition, it is preferable because the area where the conductor pattern is provided can be increased. Of course, the electromagnetic conversion efficiency also increases.

The conductor pattern serving as a coil may have a simple one-turn structure as shown in FIG. 2 or a plural-turn structure. An example of two turns is shown in FIG. On the surface of the resin film 20, two coils 22 each having a conductor pattern arranged in parallel are formed. In the case of a multi-turn configuration, the center line of the neutral zone should be distributed as close as possible (symmetrically) to the left and right. Coil 22 and permanent magnet plate 1 for 2 turns
The relationship with the magnetic pole of 0 is shown in FIG. By making such a relationship, the vibration caused by the force component parallel to the surface, which occurs in the conductor pattern at the position deviated from the center line of the neutral zone, is canceled out, and the vibrating membrane vibrates as efficiently as possible in the direction perpendicular to the surface. Can be made.

As shown in FIG. 5A, the vibrating membrane may have a structure in which the coil 22 is formed on one side of the resin film 20, or the coil 22 may be formed on both sides of the resin film 20 (B in FIG. 5). reference). Depending on the case, as shown in FIG. 5C, the resin film 20 with the coil 22 is attached.
A configuration in which a plurality of sheets are stacked and arranged by folding back is also possible. However, when stacking resin films with coils formed on both sides, another insulating film may be interposed between
It is necessary to take measures such as applying insulation treatment to the coil surface.

FIG. 6 is an explanatory view showing another embodiment of the thin electromagnetic converter according to the present invention. The embodiment shown in FIG. 6A is
It is a single-sided drive type of a permanent magnet plate. The cushioning member 1 made of a plurality of nonwoven fabrics is provided on one side (lower side in the figure) of the vibrating membrane 12.
4, the permanent magnet plate 10 is arranged, the multi-sided pressing plate 60 is arranged on the opposite side (upper side in the figure) via the cushioning member 14 made of a plurality of nonwoven fabrics, and the four corners are fixed by the supporting members 16. . In FIG. 6, most of the cushioning member 14 is omitted in order to make the drawing easy to understand, but in reality, it is approximately the same size as the vibrating membrane. Here, it goes without saying that the vibrating membrane 12 and the cushioning member 14 are not fixed to the surroundings and can be freely displaced in the vertical direction as a whole. Although not shown, it is preferable to provide a high-permeability magnetic plate on the lower surface side of the permanent magnet plate 10.

The present invention has various other applications. For example, when applying multi-pole magnetization to both sides of a permanent magnet plate,
As shown in FIG. 6B, the vibrating membranes 12 may be arranged on both sides of the permanent magnet plate 70. That is, the cushioning members 14 are arranged between the permanent magnet plate 70 and the vibrating membrane 12 and between the vibrating membrane 12 and the multi-hole holding plate 60, and are fixed by the support members 16 at the corners. The fixing method is the same as that in each of the above-described embodiments, and the permanent magnet plate 70 is fixed.
While the pressing plate 60 is fixed, the vibrating membrane 12 and the cushioning member 14 can be freely displaced in the thickness direction. Further, as shown in FIG. 6C, instead of this multi-hole holding plate,
It is also possible to provide another permanent magnet plate 10.

Since the structure shown in FIG. 6A requires only one permanent magnet plate, the generated sound pressure is small, but the structure is simple and has the advantage of being lightweight and thin. In the configuration of FIG. 6B, both vibrating membranes can be driven simultaneously. In C of FIG. 6,
It is slightly thick, but the generated sound pressure can be increased.

The permanent magnet plate used in the present invention may be any permanent magnet plate other than the sintered ferrite magnets described in the above embodiments. For example, a rare earth-based permanent magnet, a neodymium-iron-boron (Nd-Fe-B) -based permanent magnet, or another metal-based magnet may be used. It may be a sintered or solid permanent magnet, or a resin-hardened plastic magnet. In the configuration in which a plurality of permanent magnet plates are arranged,
You may combine different types of permanent magnet plates. For example, a configuration is possible in which a sintered magnet is used for the main part and a plastic magnet is used for the sub part. Alternatively, one permanent magnet plate may be formed by bonding a plurality of different types of permanent magnet plates together.

The shape of the permanent magnet plate, in other words, the shape of the electromagnetic converter may be a square structure such as a square or a rectangle, or a circle or an ellipse. Of course, other arbitrary shapes may be used. Since it is thin, it is possible to have not only a flat plate shape but also an arbitrary curved surface shape (for example, a swollen curved surface shape or a bent corrugated surface shape). The total thickness is appropriately determined according to the structure, usage condition, required performance and the like. The size of each pole (magnetization size) and the pole pitch in the strip-shaped parallel magnetization pattern may be appropriately determined in accordance with the usage state, required performance, and the like.

The vibrating membrane may be composed of one sheet as described above, or may be composed of a plurality of laminated sheets. Usually, a flexible copper clad print film is photo-etched to produce a vibrating film having a desired coil pattern. The coil integrated with the resin sheet by such a printed wiring technique may have a one-turn configuration or a multi-turn configuration. Further, the coil may be formed on both upper and lower surfaces of the resin sheet. In that case, it is possible to connect the conductive patterns on the upper and lower surfaces by a technique such as through holes. The cross-sectional shape, material, length, etc. of the conductive wire pattern to be the coil are determined and determined from the design impedance of the speaker and the like.

[0034]

Since the present invention uses the multi-pole magnetized permanent magnet plate integrally formed as described above, it can be manufactured easily and with high precision, and can have sufficient mechanical strength. Further, even a fine magnetization pattern can be formed with high accuracy.
Further, since the magnetic pole appears only on the surface facing the vibrating film, it is difficult for the magnetic force lines to pass in an unnecessary direction, the number of magnetic force lines interlinking with the coil of the vibrating film at the core is increased, and the driving efficiency is also improved. Also,
Since the magnetized pattern can be formed densely, the gap between the permanent magnet structure and the vibrating membrane can be narrowed, and in that respect as well, the conversion efficiency can be improved and the electromagnetic converter can be made thin as a whole.

In the present invention, since the vibrating membrane is supported so that it can be freely displaced in the thickness direction in the peripheral portion, a fulcrum does not occur in the peripheral portion, a reproduced sound faithful to the drive current is generated, and the amplitude is increased. There is an advantage that can be increased. Since the cushioning member made of non-woven fabric is interposed between the vibrating membrane and the permanent magnet body, the vibrating membrane does not collide with the permanent magnet body, etc., and unnecessary noise (chattering noise etc.) is prevented. it can.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of an electromagnetic converter according to the present invention.

FIG. 2 is a perspective view showing the structure and mutual positional relationship of a permanent magnet plate and a vibrating membrane.

FIG. 3 is an explanatory diagram showing another example of the vibrating film.

FIG. 4 is an explanatory view showing the structure and mutual positional relationship of a permanent magnet plate and a vibrating membrane.

FIG. 5 is an explanatory view showing another example of the vibrating film.

FIG. 6 is an explanatory diagram showing another configuration example of the electromagnetic converter according to the present invention.

[Explanation of symbols]

 10 Permanent Magnet Plate 12 Vibration Film 14 Cushioning Member 16 Supporting Member 20 Resin Film 22 Coil 30 High Permeability Magnetic Plate

Claims (4)

[Claims] 1. A permanent magnet plate, a vibrating film arranged so as to face the permanent magnet plate, a cushioning member interposed between the vibrating film and the permanent magnet plate, and a permanent magnet plate of the vibrating film. And a supporting member for regulating a relative position to the vibrating film, the permanent magnet plate has a parallel striped multi-pole magnetized pattern in which strip-shaped N poles and S poles alternately appear on almost the entire surface facing the vibrating film. The vibration film has an integrated structure in which a large number of through holes for exhaust are arranged at the position of the neutral zone in the magnetizing pattern, and the vibrating film is a thin and flexible resin film, and a coil having a meandering conductor wire pattern is printed on the wiring. In this structure, the linear portion of the conductor wire pattern is provided at a position corresponding to the neutral zone of the permanent magnet plate, and the displacement in the in-plane direction is restricted by the supporting member without being fixed at the peripheral portion. However, it is supported so that it can be freely displaced in the thickness direction, the cushioning member has a structure in which a plurality of sheets that are soft and breathable and have substantially the same size as the vibrating membrane are stacked, A thin electromagnetic converter characterized in that it is arranged so as to have a gap between a sheet and the permanent magnet plate or the vibrating membrane. 2. A permanent magnet plate and a cushioning member are respectively arranged on both sides of the vibrating film so as to sandwich the vibrating film, and both of the permanent magnet plates are such that their respective neutral zones are coincident and the same poles face each other. The thin electromagnetic converter according to claim 1, wherein the thin electromagnetic converter is fixed in a positional relationship at intervals. 3. The thin electromagnetic converter according to claim 2, wherein a vibrating film having a meandering conductive wire pattern formed on both sides of a resin film is used. 4. A high magnetic permeability magnetic plate for preventing magnetic flux leakage is adhered to the surface of the permanent magnet plate opposite to the surface facing the vibrating film, and the high magnetic permeability magnetic plate is also an exhaust formed on the permanent magnet plate. 4. The thin structure according to claim 1, wherein a large number of exhaust through holes similar to the exhaust through holes are formed so that the exhaust through holes of the permanent magnet plate and the exhaust through holes of the high-permeability magnetic plate communicate with each other. Electromagnetic converter.