JP2009267875A - Dust cap, and motor-driven speaker employing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor-driven speaker that is capable of suppressing a peek dip in playback sound pressure frequency characteristics, improves efficiency, also sufficiently improves a playback sound pressure level, and improves playback sound quality, regarding the motor-driven speaker comprising a voice coil including a track-shaped coil having a long-diameter direction and a short-diameter direction, and a bobbin. <P>SOLUTION: A dust cap engaged to a voice coil including a track-shaped bobbin having a long-diameter direction and a short-diameter direction and a coil wound around the bobbin. The dust cap comprises: two engagement plane parts each of which is an arcuate part of the track shape and engaged to one terminal portion of the bobbin; and a fitting-in part which extends in a recessed shape between the engagement plane parts, is fitted into an internal space defined by the bobbin, links and reinforces two inner wall planes of the bobbin defined by a set of longer sides along the long-diameter direction of the track shape. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an elongate electrodynamic speaker having a shorter minor axis direction than a major axis direction, excellent in sound reproduction capability, and suitable for being attached to a device such as a display.

  In an audio device such as a display to which a speaker for reproducing sound is attached, it is desired to reduce the space required for attaching the speaker. In particular, slender (rectangular, oval (including elliptical, track-shaped)) electrodynamic speakers have a diaphragm area limited in the minor axis direction, and are affected by the division vibration that is typical of slender speaker diaphragms. It is difficult to obtain a large and flat reproduction sound pressure frequency characteristic, and if a magnetic circuit for a speaker with a high magnetic gap magnetic flux density is used, the magnetic circuit is wider than the speaker diaphragm and cannot be reduced in size. There are disadvantages in audio playback capability for various reasons. Therefore, conventionally, various speaker diaphragms, voice coils, speaker magnetic circuits, and electrodynamic speakers using the same have been proposed to solve these problems.

  For example, conventionally, in a track type speaker in which the vertical and horizontal dimensions of the speaker shape are the long side and the short side, the magnet (3) constituting the magnetic circuit has a large shape as long as it fits within the speaker outline. Further, the pole (1) and the voice coil VC constituting the magnetic circuit are formed in an elongated shape extending in the longitudinal direction, and the width of the damper between the voice coil VC and the longitudinal side is secured. The cross-sectional area S of the pole (1) is such that when the pole shape is a circle, a track-type speaker having a cross-sectional area such as a circle and a circle having a diameter of approximately 1/3 or more than the dimension a on the short side Yes (Patent Document 1).

  In addition, for example, by suppressing abnormal vibration in the longitudinal direction and realizing sound wave radiation without abnormality for a large input, the planar shape of the vibration surface viewed from the vibration direction has a long side and a short side, The vibration surface has a curved portion that is continuous in a concavo-convex shape in the longitudinal direction, and a groove portion is integrally provided at a substantially central portion in the longitudinal direction so as to be orthogonal to the longitudinal direction of the vibration surface. A non-axisymmetric diaphragm, and an edge that is formed in a band shape along the outer periphery of the diaphragm, the inner periphery of the band is connected to the outer periphery of the diaphragm, and the diaphragm is held freely oscillating, A voice coil bobbin in which a foam portion to be wound is divided into two in the longitudinal direction of the diaphragm, the divided portions are joined to form a beam, and the beam is in contact with the back surface of the bottom of the groove portion of the diaphragm; Voice coil wound around the outer surface of the voice coil bobbin and vibration for the voice coil A magnetic circuit for giving a magnetic flux, an outer peripheral portion of the edge, there is an electro-acoustic transducer, characterized in that more structure and a frame holding the magnetic circuit (Patent Document 2).

  On the other hand, conventionally, the present invention relates to an elongated (rectangular) speaker used in audiovisual equipment such as a television, and provides a speaker with excellent sound quality having flat frequency characteristics while suppressing division resonance. As an object, at least a rectangular diaphragm, a plurality of magnetic circuits juxtaposed corresponding to the diaphragm, and a plurality of magnetic circuits inserted into the magnetic gap of the magnetic circuit and coupled to the inner periphery of the diaphragm There is a speaker composed of a support coil and a voice coil coupled to each of them (Patent Document 3).

JP 2000-197190 A (FIG. 1) JP 2002-176691 A (FIGS. 1 to 3) Japanese Patent Laid-Open No. 9-261795 (FIGS. 1-2)

  However, none of the prior art speakers are sufficient. In the voice coil speaker having the track-type bobbin described in Patent Document 1, the voice coil strength is insufficient, and problems such as resonance and generation of abnormal noise are likely to occur. The speaker described in Patent Document 2 is a special speaker having a track shape in which the outer diameter of the bobbin of the voice coil and the outer diameter of the diaphragm are substantially the same, and the voice coil is 2 in the longitudinal direction. It has to be divided into special voice coils such that the divided portions are joined to form a beam, and is not necessarily suitable for an elongated speaker in which the bobbin of the voice coil is fixed to the center of the diaphragm. In addition, the elongated speaker provided with the support portion described in Patent Document 3 is effective in suppressing split resonance, but the speaker vibration system is heavy due to its complicated shape, and as a result, efficiency and reproduction sound pressure level are increased. There is a problem that the speaker becomes low and input resistance is poor.

  The present invention has been made in order to solve the above-described problems of the prior art, and an object of the present invention is to provide a track-type bobbin having a major axis direction and a minor axis direction, and a voice coil including a track-type coil, For electrodynamic speakers with a dust cap that engages with a voice coil and an elongated speaker diaphragm with a bobbin fixed to the center, it is possible to suppress the peak dip of playback sound pressure frequency characteristics, and to improve efficiency It is an object to provide an electrodynamic speaker having a high reproduction sound pressure level and an excellent reproduction sound quality.

  The dust cap of the present invention is a dust cap that engages with a track-type bobbin having a major axis direction and a minor axis direction, and a voice coil including a coil wound around the bobbin. Two engagement plane portions that are engaged with one end of the bobbin, and a recess that extends between the engagement plane portions and is fitted into an internal space defined by the bobbin. A fitting portion that connects and reinforces two inner wall planes of the bobbin defined by a set of long sides along the major axis direction.

  Preferably, in the dust cap of the present invention, the insertion portion of the dust cap is composed of two reinforcing planes connected in a substantially V shape in the cross section in the major axis direction.

  Preferably, the dust cap of the present invention has two inner wall planes of the bobbin in which the reinforcing plane constituting the fitting portion of the dust cap extends over almost the entire range of the long side of the set along the major axis direction of the track shape. It is linked with.

  The electrodynamic speaker of the present invention is an elongated speaker diaphragm having the dust cap, a voice coil with which the dust cap is engaged, and a major axis direction and a minor axis direction connected to a bobbin of the voice coil. And a magnetic circuit having a magnetic gap in which the coil of the voice coil is disposed.

  Preferably, the electrodynamic speaker of the present invention further includes a second dust cap that is fixed to the speaker diaphragm and covers the dust cap and the voice coil when the speaker diaphragm is viewed from the front.

  The operation of the present invention will be described below.

  The electrodynamic speaker according to the present invention includes a track-type coil having a major axis direction and a minor axis direction, a voice coil including a track-type bobbin, a dust cap that engages with the voice coil, and a bobbin fixed to the center thereof. An electrodynamic speaker comprising an elongated diaphragm and a magnetic circuit having a magnetic gap in which a coil of a voice coil is disposed. The dust cap is a track-shaped arcuate part that is engaged with one end of the bobbin, and an internal space defined by the bobbin that extends in a concave shape between the engaging flat parts. A fitting portion that is fitted and reinforces the two inner wall planes of the bobbin defined by a pair of long sides along the major axis direction of the track shape.

  That is, in the electrodynamic speaker of the present invention, the dust cap that engages with the track-type bobbin is connected to the inner wall plane of the track-type bobbin that tends to be weak on the long side along the major axis direction, The coil bobbin can be reinforced to suppress split resonance, and distortion and abnormal noise can be reduced. Preferably, in the dust cap of the present invention, the insertion portion is configured by two reinforcing planes connected in a substantially V shape in a cross section in the major axis direction, and the reinforcement plane constituting the insertion portion is a track-shaped major axis direction. Connected to the two inner wall planes of the bobbin over almost the entire range of the set of long sides. Therefore, only by improving the dust cap, it is possible to realize an elongated electrodynamic speaker that is excellent in reproduction sound quality that can be attached even if the space for attaching the audio equipment is narrow.

  The electrodynamic speaker of the present invention may further include a second dust cap that is fixed to the speaker diaphragm and covers the dust cap and the voice coil so that the speaker coil is not exposed when the speaker diaphragm is viewed from the front. . Specifically, the dust cap of the present invention is used as a reinforcing material for reinforcing a bobbin of a track-type voice coil. That is, the dust cap of the present invention is applied to an elongated electrodynamic speaker having a second dust cap that is exposed by being connected to the speaker diaphragm and a track-shaped voice coil that is covered on the back side by the second dust cap. In addition, it is possible to reinforce the voice coil bobbin to suppress split resonance, reduce the generation of distorted sound and abnormal noise, and provide an electrodynamic speaker excellent in reproduced sound quality.

  The dust cap of the present invention is preferably lightweight because it is made of a paper material made of paper, or a resin film material such as PP (polypropylene) or PEI (polyetherimide) formed by vacuum molding or the like. Yes, the increase in the weight of the speaker vibration system can be minimized. Therefore, even in an electrodynamic speaker using a track-type voice coil so as to secure the length of the voice coil located in the magnetic gap of the magnetic circuit, the divided vibration of the track-type bobbin is suppressed, and the efficiency and the reproduced sound are reduced. The pressure level can be increased to improve the playback sound quality and input resistance.

  An electrodynamic speaker using a dust cap according to the present invention includes a track bobbin having a major axis direction and a minor axis direction, a voice coil including a track coil, and an elongated speaker diaphragm in which the bobbin is fixed to the center. Even if it is an electrodynamic type speaker equipped with, an electrodynamic type speaker that can suppress the peak dip of the reproduction sound pressure frequency characteristics, has high efficiency and sufficiently high reproduction sound pressure level, and has excellent reproduction sound quality can do.

  The dust cap according to the present invention extends the object of the present invention to a concave shape between two engagement plane portions that are track-shaped arc portions and engage with one end of the bobbin. And a fitting portion that is fitted into an internal space defined by the bobbin and that connects and reinforces the two inner wall planes of the bobbin defined by a pair of long sides along the long-diameter direction of the track shape. It was realized by doing.

  Hereinafter, although the dust cap by the preferable embodiment of this invention and the electrodynamic speaker using the same are demonstrated, this invention is not limited to these embodiment.

  1 and 2 are diagrams illustrating an electrodynamic speaker 1 according to a preferred embodiment of the present invention. FIG. 1A is a perspective view of the electrodynamic speaker 1 as viewed from the front side obliquely upward, and FIG. 1B is a perspective view of the magnetic circuit 10 constituting the electrodynamic speaker 1 from the front side obliquely upward. FIG. 2A is a cross-sectional view in the major axis direction of the electrodynamic speaker 1 (AA ′ cross section), and FIG. 2B excludes a front dust cap 5 described later for the sake of explanation. 2 is an enlarged perspective view in which a part of the electrodynamic speaker 1 is enlarged. FIG.

  The electrodynamic speaker 1 of this embodiment is an elongated electrodynamic speaker having a track-shaped speaker diaphragm 2 having a major axis length of about 15.0 cm and a minor axis direction length of about 2.5 cm. As will be described later, a part of the structure of the electrodynamic speaker 1, the internal structure, and the like are omitted. The direction in which the straight line connecting the points A-A ′ extends is the major axis direction, and the direction in which the straight line connecting the points B-B ′ extends is the minor axis direction. The track shape is a shape formed from a set of long sides along the major axis direction and a set of arcs connecting the set of long sides, the outer peripheral end of the speaker diaphragm 2, And the inner peripheral edge part of the edge 3 has a set of long sides and a set of circular arcs which connect a set of long sides.

  The speaker diaphragm 2 having a track shape as an outer shape and an inner shape is a diaphragm made by paper-making the entire shape into an elongated cone shape. The outer peripheral end of the edge 3 is supported by an edge 3. The frame 6 is fixed. A voice coil 4 composed of a bobbin and a coil is connected to the inner peripheral end of the speaker diaphragm 2, and a dust cap 20 (described later) for reinforcing the track-shaped voice coil 4 is bonded to the upper end of the speaker coil 2. Yes. Therefore, the bobbin and coil of the voice coil 4 are also track-shaped. Further, the dust cap 20 is covered with the front dust cap 5 connected to the speaker diaphragm 2 and is not exposed when the electrodynamic speaker 1 is viewed from the front. The speaker diaphragm 2 may be a cone diaphragm formed by press molding, injection molding, or impregnating a base material with a thermosetting resin, such as PSP, PP, paper, aluminum alloy, Further, it may be a planar diaphragm formed by punching a planar material made into a thin plate.

  Further, the inner diameter end of the damper 9 is connected to the outer surface of the bobbin of the voice coil 4 with an adhesive. The outer diameter end of the damper 9 is bonded and fixed to the damper fixing portion of the frame 6. As shown in FIG. 1 (a), the damper 9 has the corrugation of the support movable part cut away in a range of about ± 45 ° from the minor axis direction in the circumferential direction, so that the corrugation of the support movable part in the major axis direction is supported. As a result, the outer surface of the bobbin of the voice coil 4 is exposed from the cut portion. The damper 9 may be a corrugation damper that is formed by impregnating a phenolic resin with a woven fabric of flexible fibers as a base material, or may be formed of other materials. For example, a butterfly damper having an arm connecting the inner ring and the outer ring and formed of metal or resin may be used.

  The frame 6 has an elongated shape corresponding to the track-shaped speaker diaphragm 2, and the magnetic circuit 10 fixed to the frame 6 also has an elongated shape having a narrow width less than the length in the minor axis direction. Specifically, the fixed portion of the frame 6 is formed of a set of long sides along the major axis direction and a set of short sides along the minor axis direction connecting the pair of long sides. The outer shape has a major axis length of about 17.0 cm and a minor axis length of about 3.0. Parts constituting the vibration system such as the voice coil 4 are exposed from the window on the back side of the frame 6. Therefore, the electrodynamic speaker 1 is a speaker suitable for a device having a small width for mounting the speaker, such as a side portion of a display unit included in a device such as a display. A terminal 7 is attached to the frame 6. As will be described later, the tinsel wire 8 to be soldered to the terminal 7 connects the terminal 7 and the lead wire of the coil 4 of the voice coil 4. Supply audio current to the coil.

  The magnetic circuit 10 includes an elongated top plate 11 fixed to the frame 6, and a center pole 12 that is inserted into a track-shaped hole formed in the center of the top plate 11, which has a track-shaped long cylindrical shape. And an elongated under plate 14 in which the center pole 12 is disposed in the center, and a magnet 15 sandwiched between the top plate 11 and the under plate 14. The top plate 11 and the center pole 12 form a track-shaped magnetic air gap 13 having an equal width. That is, the magnetic circuit 10 is an outer magnet type magnetic circuit having a track-shaped magnetic gap 13, and the major axis direction and minor axis direction of the magnetic circuit 10 are the same as the major axis direction and minor axis direction of the track-shaped speaker diaphragm 2. I'm doing it.

  The voice coil 4 is formed of a bobbin formed in a long cylindrical shape having a track-shaped cross section, and a coil that is wound around one end thereof and supplied with an audio current. The bobbin is connected to the inner peripheral end of the speaker diaphragm 2 by an adhesive at the outer side surface close to the other end side where the coil is not wound. The voice coil 4 is supported so as to be able to vibrate by a damper 9 and an edge 3 via a speaker diaphragm 2, and the track-shaped coil is disposed in the track-shaped magnetic gap 13 of the magnetic circuit 10. The major axis direction length of the coil is about 22.0 mm, the minor axis direction length is about 7.0 mm, and the radius of the track-shaped arc is about 3.5 mm.

  Therefore, the speaker vibration system including the speaker diaphragm 2, the edge 3, the voice coil 4, the front dust cap 5, the dust cap 20, and the damper 9 is supported so as to be able to vibrate with respect to the frame 6. In the electrodynamic speaker 1, when a voice current is supplied to the coil of the voice coil 4 through the terminal 7 and the tinsel wire 8, a driving force is applied to the voice coil 4 disposed in the magnetic gap 13, and the voice coil 4 moves back and forth. The connected speaker diaphragm 2 also vibrates in the front-rear direction. In the electrodynamic loudspeaker 1, front and rear refers to the side where the voice coil 4 and the magnetic circuit 10 are attached when the speaker diaphragm 2 vibrates, and the speaker diaphragm 2 and the front dust cap. The side where 5 is exposed is the front side.

  The dust cap 20 is a member bonded to the upper end side of the bobbin of the voice coil 4, and is a magnetic circuit in which the coil of the voice coil 4 vibrates inside the electrodynamic speaker 1 through the space inside the voice coil 4. This prevents the track-shaped foreign matter such as iron powder from entering the 10 magnetic gaps 13. The dust cap 20 in the present embodiment is a paper material having a thickness of about 0.3 mm. In addition, PSP, PP, aluminum alloy or the like is press-molded, injection-molded, or thermoset on a base material. It may be a member that is impregnated with a functional resin and molded. Further, as will be described later, the dust cap 20 is a member that reinforces the track-type voice coil 4 that tends to be weak, suppresses the division resonance of the speaker vibration system of the electrodynamic speaker 1, distorted sound, and Reduce the occurrence of abnormal noise.

  The dust cap 20 includes two engaging flat portions 21 and two reinforcing flat surfaces 22, and has a shape in which one strip is bent into a substantially V shape. That is, in the dust cap 20, the fitting portion that extends in a concave shape between the two engagement plane portions 21 is formed in a substantially V shape in the cross section in the major axis direction by the two reinforcing planes 22. The V-shaped part is inserted into the internal space of the track-shaped voice coil 4. Specifically, the dust cap 20 that is a paper material that has been paper-made may be formed in a three-dimensional substantially V-shape at the paper-making stage, or may be formed by folding a paper material that has been made into a flat shape. Good.

  The engaging flat surface portion 21 is longer than the radius of the track-shaped arc portion of the bobbin of the voice coil 4 in the long diameter direction so as to engage with the bobbin of the track-shaped voice coil 4 having the long diameter direction and the short diameter direction. Is longer (about 3.9 mm) and has a width (about 6.95 mm) substantially equal to the inner dimension of the bobbin of the voice coil 4 in the minor axis direction in the minor axis direction. Therefore, the engagement flat surface portion 21 only needs to have an area that substantially covers the track-shaped arc portion of the bobbin of the voice coil 4. In the engagement flat surface portion 21 of the present embodiment, as shown in FIG. Thus, it is defined as a plane in which part of the corners of the rectangle are connected by an arc.

  On the other hand, as shown in FIG. 2B, the reinforcing plane 22 is a plane extending obliquely downward so as to approach the magnetic circuit 10 from the engaging plane portion 21 toward the center O side in the major axis direction. The two reinforcing planes 22 respectively extending from the two engaging plane portions 21 are crossed and connected on the axis of the center O to form a substantially V-shaped fitting portion in the cross section in the major axis direction. . Therefore, the reinforcing plane 22 is defined by two inner wall planes of the bobbin defined by a set of long sides along the track-shaped major axis direction of the bobbin of the voice coil 4, that is, inside the bobbin corresponding to the long side of the track-shaped. Connect and reinforce the flat parts. Since the dust cap 20 is bonded to the voice coil 4 with an adhesive, the two inner wall planes of the bobbin are connected by applying an adhesive to the end surface in the short diameter direction of the reinforcing plane 22 connected to the voice coil 4. To do.

  In the case of the dust cap 20 of the present embodiment, the position of the broken ridge line defined by the engagement flat surface portion 21 and the reinforcing flat surface 22 is the long side of the track shape of the bobbin of the voice coil 4 in the cross section in the major axis direction. Almost coincides with the position of the boundary line between the arc and the arc. That is, the engaging flat surface portion 21 of the dust cap 20 corresponds to the track-shaped arc portion of the bobbin of the voice coil 4, while the reinforcing flat surface 22 of the dust cap 20 is the long side of the track-shaped bobbin of the voice coil 4. Corresponds to the part. Therefore, the reinforcing plane 22 is connected to the two inner wall planes of the bobbin over substantially the entire range of the long side of the set along the major axis direction of the track shape. Strength can be strengthened.

  The reinforcing plane 22 of the present embodiment extends obliquely at an angle of about 45 ° from the engaging plane portion 21 in the downward direction. Therefore, in the vicinity of the center O, the two reinforcing planes 22 intersect at an angle of about 90 °, and the depth from the engagement plane portion 21 at the apex where the two reinforcing planes 22 intersect is the same as that of this embodiment. In this case, it is about 18.5 mm. The depth of the substantially V-shaped fitting portion can be changed in various ways depending on the above angle and the track shape of the bobbin of the voice coil 4, and preferably the damper 9 is bonded to the bobbin of the voice coil 4. It should be as deep as possible. Even when the position of the vertex where the two reinforcing planes 22 intersect is deep, even if the speaker vibration system of the electrodynamic speaker 1 vibrates, it does not contact the upper end surface of the center pole 12 of the magnetic circuit 10. As described above, a sufficient distance from the upper end surface of the center pole 12 may be provided.

  The electrodynamic speaker 1 of this embodiment includes a front dust cap 5 for adjusting sound quality, in addition to a dust cap 20 for dust-proofing the magnetic gap 13 and reinforcing the voice coil 4. The front dust cap 5 is an elongated member formed of a paper material that is formed into a convex shallow dome shape on the front surface, corresponding to the elongated speaker diaphragm 2, and is separated from the dust cap 20 to be a speaker. It adheres to the diaphragm 2 with an adhesive and covers the dust cap 20 and the voice coil 4 so as not to be exposed. By providing the front dust cap 5 separately from the dust cap 20, the disturbance of the reproduction sound pressure frequency characteristic due to the dent effect in the cone-shaped speaker diaphragm 2 is reduced, and the high frequency tone of the reproduced sound is vibrated by vibration. Can be adjusted. Therefore, since the electrodynamic speaker 1 of the present embodiment is dust-proof by the dust cap 20, it may be used without the front dust cap 5.

  FIG. 3 is a diagram for explaining conventional electrodynamic speakers 31 and 41 as comparative examples, each of which is a cross-sectional view in the major axis direction. The electrodynamic speakers 31 and 41 of the comparative example are elongated speakers having substantially the same configuration as the electrodynamic speaker 1 of the present embodiment, and do not include the dust cap 20 described above, and the front dust cap 5 Except for the point provided with the dust cap 35 or 45 instead of, the other configuration is the same as that of the electrodynamic speaker 1 of the present embodiment. Accordingly, common parts are denoted by common numbers and description thereof is omitted.

  As shown in FIG. 3A, the electrodynamic speaker 31 of the comparative example includes a dust cap 35 that is connected to the upper end side of the bobbin of the track-type voice coil 4. The dust cap 35 is a thin dome shape that is elongated and convex on the front surface, and does not have a substantially V-shaped fitting portion that the dust cap 20 has. Therefore, there is no structure that reinforces the two inner wall planes of the bobbin of the track-type voice coil 4, and the bobbin of the voice coil 4 is likely to cause split resonance as compared with the case of this embodiment.

  The electrodynamic speaker 41 of the other comparative example does not include a dust cap connected to the upper end side of the bobbin of the track-type voice coil 4 as shown in FIG. A dust cap 45 connected to the diaphragm 2 is provided. Since the dust cap 45 is connected to the speaker diaphragm 2, it does not have a structure for reinforcing the two inner wall planes of the bobbin of the track-type voice coil 4. Therefore, compared to the case of the present embodiment, the bobbin of the track-type voice coil 4 tends to cause split resonance.

  FIG. 4 shows on-axis 1 m sound pressure frequency characteristics, second and third harmonic distortion characteristics, and electrical impedance characteristics of the electrodynamic speaker 1 having the speaker vibration system including the dust cap 20 of the present embodiment. It is a graph. Since the electrodynamic speaker 1 of the present embodiment includes the dust cap 20, the vicinity of about 1.5 kHz and about 8 kHz that are likely to occur when the track-type voice coil 4 and the elongated speaker diaphragm 2 are combined. By suppressing the divided vibration at, smooth sound pressure frequency characteristics and a low harmonic distortion factor (particularly third-order distortion) can be realized. In addition, since the electrodynamic speaker 1 of this embodiment uses the front dust cap 5 for adjusting the sound quality that realizes the above frequency characteristics, a high reproduction sound pressure level is realized even in a high sound range of about 8 kHz or more. ing. That is, as can be seen from comparison with a comparative example described later, an electrodynamic speaker having high efficiency and excellent reproduction sound quality is realized while being an elongated speaker.

  FIG. 5 is a graph showing on-axis 1 m sound pressure frequency characteristics, second and third harmonic distortion characteristics, and electrical impedance characteristics of an electrodynamic speaker 31 having a dust cap 35 of a comparative example. Since the electrodynamic speaker 31 does not include the dust cap 20, the divided vibration that is likely to be generated by the combination of the track-type voice coil 4 and the elongated speaker diaphragm 2 is remarkably generated. In the vicinity of .5 kHz and about 8 kHz, a peak dip of the sound pressure frequency characteristic and a harmonic distortion rate (particularly third-order distortion) that becomes remarkably high are observed. In addition, the reproduction sound pressure level in the high sound range of about 8 kHz or more is lowered, and the electrodynamic speaker is inferior in reproduction sound quality as compared with the electrodynamic speaker 1 of the present embodiment.

  FIG. 6 is a graph showing on-axis 1 m sound pressure frequency characteristics, second and third harmonic distortion characteristics, and electrical impedance characteristics of the electrodynamic speaker 41 including the dust cap 45 of the comparative example. Since this electrodynamic speaker 41 also does not include the dust cap 20, the divided vibration that is likely to be generated by the combination of the track-type voice coil 4 and the elongated speaker diaphragm 2 is remarkably generated. In the vicinity of .5 kHz, a harmonic distortion rate (particularly third-order distortion) that is remarkably high is observed. Although the reproduction sound pressure level in the high frequency range of about 8 kHz or more is increased by providing the dust cap 45, the electrodynamic speaker is inferior in reproduction sound quality as compared with the electrodynamic speaker 1 of this embodiment. .

  Therefore, the electrodynamic speaker 1 of the present embodiment is configured such that the bobbin of the track-shaped voice coil 4 is fixed to the center of the track-shaped speaker diaphragm 2 by making the shape of the dust cap 20 as described above. Even so, the intensity of the bobbin of the track-shaped voice coil 4 can be increased to suppress the divided vibration, and a flat reproduction sound pressure frequency characteristic and a low harmonic distortion factor can be obtained. That is, the dust cap 20 is inserted into an internal space defined by the bobbin extending in a concave shape between the two engaging plane portions and the engaging plane portions, and a set of tracks along the major axis direction of the track shape. And a fitting portion that connects and reinforces the two inner wall planes of the bobbin defined by the long side, so that the coil length of the voice coil 4 located in the magnetic gap 13 of the magnetic circuit 10 is made track-shaped. Even if one is employed and secured, the divided vibration of the voice coil 4 can be suppressed. In addition, increasing the efficiency and playback sound pressure level, which tend to decrease with slender electrodynamic speakers, results in the need to input excessive audio signal power and increase the rated input. It is possible to realize an electrodynamic speaker that is superior in voice and has improved input resistance and quality.

  The dust cap 20 constituting the electrodynamic speaker of the present invention is not limited to the shape in the above embodiment, and for example, a connecting portion 23 (not shown) that connects the two engaging flat portions 21 in the same plane. ), Which engages with the upper end surface of the bobbin of the track-type voice coil 4 (that is, the long side portion of the track-type). The strength of the voice coil 4 is further increased, and the occurrence of divided vibration can be suppressed. Further, the front dust cap 5 of this embodiment is separated from the dust cap 20, but the front dust cap 5 is fixed to the speaker diaphragm 2, and covers the dust cap 20 so that it is not exposed to the front. If present, the front dust cap 5 and the dust cap 20 may be bonded with an adhesive.

  The electrodynamic speaker of the present invention is not limited to a track-shaped speaker diaphragm and a speaker using a track-shaped voice coil, and is driven by an elongated diaphragm that emits sound waves, and the elongated diaphragm. The present invention can also be applied to other electric-mechanical-acoustic transducers having other vibration systems in which a driving member that transmits force has a combination of elongated shapes.

It is a figure explaining the electrodynamic speaker 1 by preferable embodiment of this invention. Example 1 It is a figure explaining the electrodynamic speaker 1 by preferable embodiment of this invention. Example 1 It is a figure explaining the electrodynamic type speakers 31 and 41 of a comparative example. It is a graph showing the 1-m sound pressure frequency characteristic on an axis | shaft of the electrodynamic speaker 1 by preferable embodiment of this invention, etc. FIG. Example 1 It is a graph showing the 1-m sound pressure frequency characteristic on an axis of the electrodynamic type speaker 31 of a comparative example, etc. It is a graph showing the 1-m sound pressure frequency characteristic on the axis of the electrodynamic type speaker 41 of a comparative example, etc.

Explanation of symbols

1, 31, 41 Electrodynamic speaker 2 Speaker diaphragm 3 Edge 4 Voice coil 5 Front dust cap 6 Frame 7 Terminal 8 Kinshi wire 9 Damper 10 Magnetic circuit 11 Top plate 12 Center pole 13 Magnetic gap 14 Under plate 15 Magnet 20 Dust Cap 21 Engagement plane 22 Reinforcement plane 35, 45 Dust cap

Claims (5)

A dust cap that engages a track-type bobbin having a major axis direction and a minor axis direction, and a voice coil including a coil wound around the bobbin,
The dust cap is an arc-shaped portion of the track shape, and is engaged with one end of the bobbin. The dust cap extends in a concave shape between the engagement flat surface portions. A fitting portion that is fitted into a defining internal space and connects and reinforces two inner wall planes of the bobbin defined by a pair of long sides along the major axis direction of the track shape,
Dust cap. The fitting portion of the dust cap is composed of two reinforcing planes connected in a substantially V shape in the cross section in the major axis direction.
The dust cap according to claim 1. The reinforcing plane constituting the fitting portion of the dust cap is connected to the two inner wall planes of the bobbin over almost the entire range of a set of long sides along the major axis direction of the track shape. ing,
The dust cap according to claim 2.   4. An elongate having the dust cap according to any one of claims 1 to 3, the voice coil with which the dust cap is engaged, and the major axis direction and the minor axis direction connected to the bobbin of the voice coil. An electrodynamic speaker comprising: a speaker diaphragm having a shape; and a magnetic circuit having a magnetic gap in which the coil of the voice coil is disposed.   The electrodynamic speaker according to claim 4, further comprising a second dust cap that is fixed to the speaker diaphragm and covers the dust cap and the voice coil when the speaker diaphragm is viewed from the front.