Suspension and electro-acoustic transducer using the suspension

A suspension with a plurality of roll sections each of which has a semi-cylindrical shape from a cross-section view. The roll sections are disposed side by side based on a straight line connecting two points on an inner periphery or an outer periphery. The roll sections form a closed loop in a manner that a roll section of the roll sections being disposed first adjoins a roll section of the roll sections being disposed last. Adjacent roll sections are coupled with each other through a boundary section forming a continuous three dimensional curved surface. A linearity of compliance improves, and generation of distortion or rolling is restricted using the suspension.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a suspension used in an apparatus for reproducing a sound such as a voice, music or a dial tone, and an electro-acoustic transducer using the same.

2. Description of the Related Art

A conventional electro-acoustic transducer is demonstrated hereinafter with reference toFIGS. 8,9A and9B.FIG. 8is a sectional view of the electro-acoustic transducer.FIG. 9Ais a plan view of a diaphragm.FIG. 9Bis a sectional view ofFIG. 9Ataken along the line9B-9B. InFIG. 8, diaphragm6generates aerial vibration. Diaphragm6is fixed to frame11by frame fixing part4through suspension1which has vibrating functions and supporting functions. Suspension1is of a semicylindrical shape in a cross section and uniform in a circumference direction. Diaphragm6is coupled with voice coil10. Voice coil10is placed within magnetic gap9of magnetic circuit8which is provided at the middle of the frame11and formed of plate13, magnet14and yoke15.

Furthermore, protector12, for protecting diaphragm6, is bonded by using an adhesive. An operation of an electromotive loudspeaker structured as disclosed above is described hereinafter.

When a current flows in voice coil10, the current crosses a magnetic field in magnetic gap9at right angles, and a driving force generated at voice coil10is transmitted to diaphragm6. Then suspension1supports voice coil10in a manner that voice coil10becomes concentric with plate13, and works as a spring in a vibrating direction when diaphragm6vibrates. When an alternating current (e.g., a voice signal) flows in voice coil10, voice coil10and diaphragm6vibrate while being supported by suspension1. As a result, air vibrates and a compressional wave is generated, so that a sound can be heard. For example, Japanese Patent Unexamined Publication (H5-103395) is known as a related art of this invention.

However, the conventional suspension has a uniform disk shape in a circumference direction and a closed structure. Therefore, as shown in an arbitrary point P ofFIG. 5, which is a sectional view of the suspension in vibration and demonstrated later, when the suspension vibrates by ΔX, a radius of point P changes by Δr, so that force is generated in a circumference direction.

This force is easy to be generated according as the suspension vibrates at large amplitude. As shown in line “A” ofFIG. 4, which is a force-displacement characteristic and demonstrated later, compliance becomes non-linear at the large amplitude. Non-linearity of the compliance of supporting force, which is caused by a shape of suspension1, causes distortion particularly in reproduction of a low tone area where amplitude becomes large.

Compliance of the suspension becomes difficult to maintain due to the phenomena discussed above, so that harmonic distortion is generated at sound pressure frequency characteristics. In addition, a deformation of the suspension is also induced, thereby causing a rolling phenomenon of the diaphragm.

SUMMARY OF THE INVENTION

A suspension includes a plurality of roll sections each of which has a semicylindrical shape in a cross section. The roll sections are disposed side by side based on a straight line connecting two points on an inner periphery or an outer periphery. The roll sections form a closed loop in a manner that a roll section of the roll sections being disposed first adjoins a roll section of the roll sections being disposed last. Adjacent roll sections are coupled with each other through a boundary section forming a continuous three dimensional curved surface.

DETAILED DESCRIPTION OF THE INVENTION

Exemplary embodiments of suspensions of the present invention are demonstrated hereinafter with reference toFIG. 1throughFIG. 7B. In the description, the same elements used in the background art have the same reference marks, and the descriptions of those elements are omitted here.

First Exemplary Embodiment

The first exemplary embodiment of the present invention is demonstrated hereinafter with reference toFIG. 1throughFIG. 5.

FIG. 1Ais a plan view of a suspension in accordance with the first exemplary embodiment of the present invention.FIG. 1Bis a sectional view ofFIG. 1Ataken along the line1B-1B.FIG. 2Ais a perspective view ofFIG. 1A.FIG. 2Bis an enlarged sectional view ofFIG. 2Ataken along the line2B-2B.FIG. 2Cis an enlarged sectional view ofFIG. 2Ataken along the line2C-2C.FIG. 3is a sectional view of an electro-acoustic transducer using the suspension.FIG. 4is a graph showing a force-displacement characteristic of the suspension in vibration.FIG. 5shows a condition of the suspension in vibration.

InFIGS. 1A and 1B, roll sections1bare disposed radially at a periphery of diaphragm6so as to form suspension1a. Connecting part3, which is linearly formed, is arranged between frame fixing part4and vibration system fixing part5is formed linear. Adjacent roll sections1bare coupled with each other through boundary section2which forms a continuous three dimensional curved surface. Non-continuous parts of connecting parts3between frame fixing part4and vibration system fixing part5are trimmed, so that connecting parts3forms a closed loop. Because a plane of vibration is structured as a circle, an ellipse, or a polygon such as a quadrilateral or a rectangle in its plan view, roll section1bis not limited in size or arrangement.

When each roll section1bhas the same shape, roll sections1bare disposed at regular intervals, thereby forming a closed loop. Adjacent roll sections1bare coupled with each other through boundary section2which forms a continuous three dimensional curved surface. Non-continuous parts of connecting parts3between frame fixing part4and vibration system fixing part5are trimmed, so that connecting parts3form a closed loop. Referring toFIG. 8, an outer periphery part of suspension1ais fixed to frame11by frame fixing part4, and an inner periphery part thereof is fixed to diaphragm6or voice coil10by vibration system fixing part5.

Because connecting part3of roll section1bis linear, force caused by the generation of Δr inFIG. 5is not generated in lateral direction. Because of deformation of a semicylindrical shape of roll section1bin vibration, boundary section2accommodates stress generated at a boundary between adjacent roll sections1b. Therefore, as shown in “B” at large amplitude of the force-displacement characteristic ofFIG. 4, a superior linearity of compliance can be obtained even at large amplitude, so that unnecessary resonance can be restricted. In addition, boundary section2covers a gap between roll sections1b, so that dust can be prevented at magnetic gap9.

Besides, a sectional shape of boundary section2between roll sections1bis not limited to a semicylindrical shape shown inFIG. 2C.

The outer periphery part of the suspension is fixed to the roll sections forming a closed loop, and non-continuous parts are trimmed, so that the suspension is formed. Connection between the roll sections and the inner periphery part is trimmed, so that generation of distortion or the like is prevented.

In addition, frame fixing part4, which is a connecting part between an outer linear portion of roll section1band frame11, is trimmed to be formed as a continuous shape and fixed to frame11.

Furthermore, vibration system fixing part5, which is a connecting part between an inner linear portion of roll section1band diaphragm6, is trimmed to be formed as a continuous shape and fixed to diaphragm6or voice coil10.

According to the first exemplary embodiment, an odd number of roll sections1bare described. Because the roll sections disposed at a periphery are formed asymmetric, generation of rolling in driving is prevented when the suspension is mounted in an electro-acoustic transducer.

Using the structure discussed above, amplitude becomes stable, so that deformation, which causes the rolling phenomenon, of suspension1acan be prevented. As a result, distortion which affects acoustic characteristics can be reduced.

In addition, suspension1amay be formed by heat-molding of a polymer resin film or thermoplastic elastomer film, or formed by injection-molding of resin. Using the method mentioned above, a complicated shape is easy to be formed, and suspension1acan be integrally molded with diaphragm6, so that the number of manufacturing processes can decrease.

Furthermore, suspension1amay be formed by weaving vegetable fiber and/or chemical fiber, impregnating resin and press-molding. In addition, suspension1amay be formed by heat-molding a sliced sheet of polyurethane form which is obtained after chemical reaction of mixing of isocyanate and polyol. Besides, suspension1amay be formed by vulcanizing unvulcanized compositions such as NBR, SBR or EPDM, which are pliable material, using heat press. Using suspension1adiscussed above, deformation can be prevented and a linearity of compliance can be obtained.

According to the first embodiment, suspension1ais coupled with diaphragm6, however, suspension1amay be fixed to voice coil10.

Furthermore, according to the first embodiment, roll section1bis formed based on a straight line connecting two points on an outer periphery, however, roll section1bmay be formed based on a straight line connecting two points on an inner periphery.

Second Exemplary Embodiment

The second exemplary embodiment of suspension device20of the present invention is demonstrated hereinafter with reference toFIGS. 6A and 6B.

FIG. 6Ais a plan view of suspension device20in accordance with the second exemplary embodiment of the present invention.FIG. 6Bis a sectional view ofFIG. 6Ataken along the line6B-6B.

Only different point between the first embodiment and the second embodiment is described hereinafter with reference toFIGS. 6A and 6B. Suspensions1cand1deach have the same shape as suspension1a, and are fixed to voice coil10. Suspension1cis placed above suspension1dat a certain distance. Suspension device20has suspensions1cand1d. Suspension1cmay be fixed to or integrally molded with diaphragm6.

Third Exemplary Embodiment

The third exemplary embodiment of suspension device20of the present invention is demonstrated hereinafter with reference toFIGS. 7A and 7B.

FIG. 7Ais a plan view of suspension device20in accordance with the third exemplary embodiment of the present invention.FIG. 7Bis a sectional view ofFIG. 7Ataken along the line7B-7B. Suspension device20has suspensions1cand1d. Suspensions1cand1deach have the same shape as suspension1a, and suspension1cis shifted from suspension1dby approximately ½ of width “L” of the roll section in a rotating direction (i.e., a periphery direction).

In other words, suspensions1cand1dare disposed in a substantially vertical direction, and one of suspensions1cand1dis rotated by ½ of a width of the roll section with respect to an axis in the periphery direction. Generation of rolling in driving can be prevented when the suspension is mounted in an electro-acoustic transducer.

Suspensions1cand1dare fixed to voice coil10and spaced each other. Suspension1cmay have the same direction as suspension1dor have a reverse direction of suspension1d. Using the structure discussed above, rigidity of suspension device20increases and rolling is further prevented.

According to the second and third embodiments, upper suspension1cis fixed to the diaphragm, however, suspension1cmay be coupled with voice coil10.

In addition, rolling is further prevented by widening interval “d” between suspensions1cand1d.

INDUSTRIAL APPLICABILITY

The present invention provides a suspension where stress generated at its inside in a circumference direction is individually divided. Using this structure, a superior linearity of compliance can be obtained, distortion which affects acoustic characteristics can be reduced and rolling caused by deformation can be restricted. As a result, the suspension which is suitable for large amplitude and has supporting functions can be obtained. Therefore, an electro-acoustic transducer which can expand low-tone-reproducing bands by reducing a minimum resonance frequency is provided, even when it is structured with the same width as a conventional one.