JP6989751B2 - Dust cap and electrokinetic speaker using it - Google Patents

Description

Application of Article 30, Paragraph 2 of the Patent Act (1) Hi-Fi Audio System NF-07 premium Exhibition / Demonstration (January 28, 2017-March 22, 2017) (2) Homepage of Rashlan Co., Ltd. (Http: //rushrun.co.jp/index.html), Hi-Fi Audio System NF-07 premium page (http://rushrun.co.jp/nf07premium_about.html) // rushrun.co.jp/nf07premium_speaker.html)

The present invention relates to a dust cap used for a voice coil provided in an electrodynamic speaker and a magnetic gap portion of a magnetic circuit, and in particular, even a full-range type speaker has excellent acoustic radiation characteristics near the high frequency limit frequency. Regarding the dust cap that realizes a type speaker.

In an electrodynamic speaker that reproduces audio, an audio signal current is supplied to the coil of the voice coil connected to the diaphragm. Since the coil is arranged in the magnetic void of the magnetic circuit, the voice coil and the diaphragm are vibrated by the driving force corresponding to the voice signal current generated by the DC magnetic field, and the voice signal is converted into a sound wave. In a general electrodynamic speaker, the voice coil is configured by winding a coil around a bobbin having a substantially cylindrical shape, and the inner diameter portion of a cone-shaped diaphragm is often connected to the outer curved surface of the bobbin. ..

In an electrodynamic speaker, if the vicinity of the magnetic gap of the magnetic circuit and the part where the voice coil of the diaphragm is connected are exposed, foreign matter may enter the magnetic gap and cause malfunctions such as abnormal noise. There is. Therefore, in many electrodynamic speakers, a dust cap is attached so as to cover the upper end surface of the bobbin of the voice coil or the portion to which the voice coil of the diaphragm is connected to prevent malfunction. The dust cap is generally required for electrodynamic speakers manufactured using a voice coil holder, which is a manufacturing jig that determines the position of the voice coil in the magnetic void. The dust cap is sometimes called the center cap.

The dust cap is a member that is attached to the voice coil and the diaphragm and vibrates integrally as a vibration system, and has a certain area compared to the diaphragm, so it has excellent acoustic radiation characteristics like the diaphragm. Is desired. For example, the dust cap is made of a material equivalent to a diaphragm that is lightweight and has a large internal loss, and its shape is also designed so that the rigidity is increased so that the divided vibration is reduced. Especially in the vicinity of the high frequency limit of the reproduction frequency band of the electrodynamic speaker, the vibration characteristic and the acoustic radiation characteristic of the dust cap have a large influence on the sound pressure frequency characteristic of the electrodynamic speaker. This is because above the high frequency limit frequency fh where the cone-shaped diaphragm vibrates separately, only the periphery of the inner diameter to which the voice coil is attached vibrates significantly, and the dust cap attached in the vicinity thereof vibrates.

In the electrodynamic speaker, various shapes of the dust cap and the configuration of the connection of the diaphragm or the voice coil with the bobbin have been conventionally proposed. For example, conventionally, the eccentric voice coil mounting portion, the first diaphragm portion defined in the direction from the inner shape center point P to the outer shape center point O, and the first diaphragm portion are substantially opposite to each other. It comprises an eccentric cone-shaped diaphragm having a defined second diaphragm portion, a bobbin attached to a voice coil mounting portion, a voice coil having a coil, and a dust cap attached to the end of the bobbin of the voice coil. , There is an electrokinetic speaker (Patent Document 1).

Further, for example, in a speaker having a diaphragm and a dust cap fixed to the diaphragm, the dust cap is a discontinuous portion in the cross-sectional shape on the surface including the central axis inside the fixed portion with the diaphragm. There is a speaker having (Patent Document 2). In addition, a magnetic circuit, a frame joined to this magnetic circuit, a voice coil inserted in the magnetic gap of the magnetic circuit, a damper whose inner circumference is coupled to the voice coil and whose outer circumference is coupled to the frame, and an inner circumference. Is a speaker coupled with a diaphragm whose outer circumference is directly or indirectly coupled to the frame and a center cap coupled to the voice coil, wherein the center cap is substantially perpendicular to the outer circumference. There is a speaker that has a cylindrical portion extending to the center, sets the inner diameter of the cylindrical portion to a diameter that fits at least the outer diameter of the upper end of the voice coil, and further connects the end of the cylinder to the diaphragm. (Patent Document 3).

In recent audio equipment, "high resolution (or high resolution)" that "exceeds the specifications of CD (compact disc)" is attracting attention. Specifically, the Japan Audio Society defines and operates logos, etc. for high-resolution audio compatible devices. As stated in it, "Speaker / headphone high-frequency reproduction performance: 40 kHz or higher is possible." In high-resolution electrodynamic speakers, the limit of the high frequency range of the human audible frequency band is reached. Sound pressure frequency characteristics far exceeding a certain 20 kHz are required. It is not enough that the sound pressure frequency characteristic is satisfied only by the measured value at 0 degrees in front of the axis of the electrokinetic speaker, but it is preferable that the sound pressure frequency characteristic is also satisfied by the directional characteristic at a predetermined angle (for example, ± 30 degrees).

In the electrodynamic speaker, the larger the diaphragm area, the better the sound reproduction in the low frequency range with a long wavelength, and conversely, the smaller the diaphragm area, the better the sound reproduction in the high frequency range with a short wavelength. Therefore, a full-range type electrokinetic speaker that tries to reproduce 20 Hz to 20 kHz, which is an extremely wide audible frequency band for humans, often has a cone-type diaphragm having a certain wide diaphragm area. There is a problem that it is very difficult to design the limit of the reproduction frequency band in the high frequency range to be 20 kHz or more. In addition to the existence of a high frequency limit frequency fh in which the cone-type diaphragm vibrates separately, in the high frequency band where the wavelength is relatively short with respect to the diaphragm area, the directional characteristics become sharp toward the front side and the directional angle. When becomes wider, the reproduction sound pressure level suddenly becomes low.

Therefore, the configuration of the dust cap becomes important in the reproduction frequency band in the high frequency range where the diaphragm vibrates separately. However, even if the conventional dust cap is simply attached so as to cover the upper end surface of the bobbin of the voice coil, or even if it is attached so as to cover the part where the voice coil of the diaphragm is connected, the ultra-high range of 20 kHz to 40 kHz. Is difficult to play on a full-range electrodynamic speaker. For example, since the conventional dome-shaped dust cap is weak in shape, only the apex portion vibrates in the region of divided vibration in the high frequency range, and the radiant energy is often insufficient.

Japanese Unexamined Patent Publication No. 2010-109665 Japanese Unexamined Patent Publication No. 2000-308180 Japanese Unexamined Patent Publication No. 2005-269604

The present invention has been made to solve the above-mentioned problems of the prior art, and an object thereof relates to a dust cap used corresponding to a voice coil provided in an electrodynamic speaker and a magnetic gap portion of a magnetic circuit. In particular, it is an object of the present invention to provide a dust cap that realizes an electrodynamic speaker having excellent acoustic radiation characteristics near the high frequency limit frequency even if it is a full range type speaker.

The dust cap of the present invention is defined on the bobbin connecting portion connected to the end of the bobbin around which the coil is wound, the first radiating portion defined on the inner peripheral side of the bobbin connecting portion, and the outer peripheral side of the bobbin connecting portion. A second radiating portion to be formed and a vibrating plate connecting portion connected to the vibrating plate on the outer peripheral side of the second radiating portion are provided. The coil is located on the back side where the coil is located and is connected to the vibrating plate. It is arranged on the front side on the opposite side, has a concave curved surface on the front side, and forms a protrusion protruding toward the front side at the intersection of two arcs on the central axis Q.

Preferably, in the dust cap of the present invention, the radius of the arc that defines the outer shape of the first radiation portion is larger than the inner diameter radius that defines the inner diameter dimension of the bobbin connecting portion, and the inner diameter is twice the inner diameter radius. Is set to a value smaller than.

Further, preferably, the electrodynamic speaker of the present invention includes the above-mentioned dust cap, a voice coil including a bobbin and a coil connected to the bobbin connecting portion of the dust cap, and a magnetic circuit having a magnetic gap in which the coil is arranged. , At least including the diaphragm connecting portion of the dust cap and the diaphragm connected to the bobbin.

Further, preferably, in the electrokinetic speaker of the present invention, the diaphragm has a cone-shaped diaphragm portion extending from the inner diameter portion defining the central hole and the outer diameter portion is located on the front side, and dust. The diaphragm connecting portion of the cap is connected so as to be substantially orthogonal to the diaphragm portion.

Hereinafter, the operation of the present invention will be described.

The dust cap of the present invention is defined on the bobbin connecting portion connected to the end of the bobbin around which the coil is wound, the first radiating portion defined on the inner peripheral side of the bobbin connecting portion, and the outer peripheral side of the bobbin connecting portion. A second radiating portion to be formed and a diaphragm connecting portion connected to the diaphragm on the outer peripheral side of the second radiating portion are provided. Therefore, the dust cap, the bobbin connected to the bobbin connecting portion of the dust cap, the voice coil including the coil, the magnetic circuit having the magnetic gap in which the coil is arranged, and the diaphragm connecting portion of the dust cap and the bobbin are connected. A diaphragm and, at least, a bobbin speaker can be configured.

In the dust cap, in the cross section including the central axis Q of the bobbin, the diaphragm connecting portion is located on the back side where the coil is located and is connected to the diaphragm with respect to the bobbin connecting portion. Therefore, the outer shape of the second radiation portion is formed like the side surface portion of the truncated cone. Further, the outer shape of the first radiation portion is concave on the front side because the center positions of at least two arcs defining the cross-sectional shape are arranged on the front side opposite to the back side of the bobbin connecting portion. It will have a curved surface. Then, the first radiation portion forms a protrusion portion protruding toward the front surface at the intersection of the two arcs on the central axis Q in the cross section.

This dust cap is sharpened so that a protrusion is formed at the center of the first radiation portion defined on the inner peripheral side of the bobbin connecting portion to form a concave curved surface on the front side. The rigidity of the first radiation portion is increased, and the split vibration in which only the protrusion portion, which is the apex, vibrates is suppressed. The radius of the arc that defines the outer shape of the first radiation portion is larger than the inner diameter radius that defines the inner diameter dimension of the bobbin connecting portion so that the protrusion protruding to the front side is firmly formed, and the inner diameter radius It is preferably set to a value smaller than the inner diameter, which is twice.

Further, in this dust cap, the concave curved surface on the front side of the first radiating portion and the curved surface of the second radiating portion formed like the side surface portion of the truncated cone have a wide pointing angle (for example, off the front on the axis). The angle will be tilted from the front in the cross section to be suitable for radiating sound waves in the direction (± 30 degrees). The area of the vibrating dust cap becomes wider by adding the area of the second radiating portion to the first radiating portion. Therefore, it can be improved as compared with the conventional case so that the difference between the frontal characteristic and the directivity of the treble range including the ultra-high range of 20 kHz to 40 kHz is reduced.

In particular, when the diaphragm extends from the inner diameter portion that defines the central hole and the outer diameter portion has a cone-shaped diaphragm portion located on the front side, an electrokinetic speaker suitable for the full range type is realized. can. The diaphragm connecting portion connected to the diaphragm on the outer peripheral side of the second radiation portion of the dust cap is connected so as to be substantially orthogonal to the vicinity of the root of the cone-shaped diaphragm. Therefore, the rigidity of the entire vibration system including the cone-shaped diaphragm, the bobbin of the voice coil, and the dust cap is increased, and the high frequency limit frequency due to the divided vibration is further increased, so that the ultra-high frequency range of 20 kHz to 40 kHz is increased. The sound pressure frequency characteristic in can be improved.

The dust cap of the present invention can realize an electrokinetic speaker having excellent acoustic radiation characteristics near the high frequency limit frequency even if it is a full-range speaker.

It is a front view and sectional drawing which shows the specific structure of the electromotive drive type speaker which concerns on one Embodiment of this invention. It is a partially enlarged sectional view which shows the specific structure of the dust cap which concerns on one Embodiment of this invention. It is a graph which shows the sound pressure frequency characteristic of the electrokinetic type speaker of this Example. It is a graph which shows the sound pressure frequency characteristic of the electrokinetic type speaker of the comparative example.

Hereinafter, the dust cap and the electrodynamic speaker according to the preferred embodiment of the present invention will be described, but the present invention is not limited to these embodiments.

FIG. 1 is a diagram illustrating an electrokinetic speaker 1 including a dust cap 10 according to a preferred embodiment of the present invention. Specifically, FIG. 1A is a front view showing the appearance of the electrokinetic speaker 1, and FIG. 1B is a cross-sectional view taken along the line AA including the central axis Q of the electrokinetic speaker 1. be. Further, FIG. 2 is a partially enlarged cross-sectional view showing a specific structure of the dust cap 10. In the following description, FIGS. 1 and 2, the description and illustration of the configuration unnecessary for the description of the present invention will be omitted. In particular, in FIG. 2, the configuration of the other electrodynamic speaker 1 of the dust cap 10 is omitted with a dotted line.

The electrokinetic speaker 1 is a full-range electrodynamic speaker having a cone-shaped diaphragm 2 and a nominal diameter of 10 cm. Therefore, it is desired to reproduce the human audible frequency band of 20 Hz to 20 kHz only by the electrodynamic speaker 1 as much as possible. Further, it is preferable that the electrodynamic speaker 1 can reproduce an ultra-high frequency range of 20 kHz to 40 kHz, which is necessary for supporting high resolution audio.

The diaphragm 2 has a cone-shaped diaphragm portion extending from an inner diameter portion defining a central hole and having an outer diameter portion located on the front surface side. In the following description, the side where the diaphragm 2 in FIGS. 1 and 2 is exposed is referred to as the front side, and the side where the magnetic circuit 8 in FIG. 1B is exposed is referred to as the back side. The diaphragm 2 of this embodiment is a diaphragm made of a paper material obtained by blending cellulose nanofibers with wood pulp and mixing them. By blending cellulose nanofibers, the diaphragm 2 has a structure in which the fibers are tightly bonded to each other, and as a result, a speaker diaphragm having an excellent Young's modulus and a wide reproduction frequency band can be obtained. ..

The outer diameter of the diaphragm 2 is oscillatedly supported by a relatively flexible edge 3. The edge 3 of this embodiment is a roll edge in which the cross section of the movable portion is convex upward. For the edge 3, an inner peripheral connecting portion is formed on the inner peripheral side of the movable portion, and an outer peripheral connecting portion is formed on the outer peripheral side of the movable portion. In the edge 3, the inner peripheral connecting portion on the inner peripheral side is adhesively fixed to the outer diameter portion of the diaphragm 2, and the outer peripheral connecting portion on the outer peripheral side is adhesively fixed to the frame 6.

The diaphragm 2 is connected by fitting a substantially cylindrical bobbin 4a of the voice coil 4 into the central hole of the inner diameter portion thereof. For the bobbin 4a of the voice coil 4, for example, a foil material having a predetermined thickness is formed into a substantially cylindrical shape, the coil 4b is wound around the lower end thereof, and the outer curved surface where the coil 4b is not wound is reinforced. The paper is rolled up and molded into a cylindrical shape as a whole. A brocade wire (not shown) is soldered and fixed to the voice coil 4, and the other end of the brocade wire is fixed so as to be conductive to the terminal 7 fixed to the frame 6. A voice signal current is supplied to the coil 4b of the voice coil 4 via these terminals 7 and a brocade wire.

The inner diameter end of the damper 5 is further connected to the outer curved surface of the bobbin 4a of the voice coil 4 with an adhesive. The outer diameter end portion of the damper 5 is adhesively fixed to the damper fixing portion of the frame 6. The damper 5 may be an annular corrugation damper formed by impregnating a woven fabric of flexible fibers with a resin such as phenol resin as a base material, and may be formed of another material. May be good. For example, it may be a butterfly damper having an arm connecting the inner peripheral side ring and the outer peripheral side ring and made of metal or resin.

The frame 6 is an iron plate frame press-molded into a basket shape, and as described above, the outer peripheral connecting portion of the edge 3, the outer diameter end portion of the damper 5, and the terminal 7 are connected. A magnetic circuit 8 is further connected to the frame 6 at the end on the back side. The frame 6 may be a basket-shaped aluminum die-cast frame or a resin frame made of resin.

The magnetic circuit 8 is composed of a ring-shaped top plate fixed to the frame 6, a pole having a center pole and a flat plate-shaped under plate, and an annular magnet, and is formed between the top plate and the pole. A circular magnetic void 9 having a uniform width is formed. The coil 4b of the voice coil 4 is supported and arranged in the magnetic gap 9 by an edge 3 and a damper 5 so that the coil 4b of the voice coil 4 can vibrate without contacting the magnetic circuit 8. The magnetic circuit 8 is not limited to the external magnetic type as in this embodiment as long as it has a predetermined magnetic gap 9 corresponding to the voice coil 4, and other magnetic circuit configurations such as an internal magnetic type are adopted. May be good.

The electrodynamic speaker 1 includes a dust cap 10. Like the diaphragm 2, the dust cap 10 is made of a paper material obtained by blending cellulose nanofibers with wood pulp and mixing them, and is a dust cap having excellent acoustic radiation characteristics. As shown in FIGS. 1 and 2, the dust cap 10 is fixed with an adhesive so as to be connected to the diaphragm 2 and the bobbin 4a of the voice coil 4.

The dust cap 10 has a bobbin connecting portion 11 connected to the end of the bobbin 4a, a first radiating portion 12 defined on the inner peripheral side of the bobbin connecting portion 11, and a second specified on the outer peripheral side of the bobbin connecting portion 11. The two radiation portions 15 and the diaphragm connecting portion 14 connected to the diaphragm 2 on the outer peripheral side of the second radiation portion 15 are provided. The bobbin connecting portion 11 is an annular portion defined by the inner diameter radius r11, and is a portion where the end portion of the bobbin 4a of the voice coil 4 is fitted and connected so as to fit on the inner diameter side. The first radiating portion 12 is a portion forming a vibration surface on the inner peripheral side of the bobbin connecting portion 11, and includes a protrusion portion 13 described later. Further, the second radiating portion 15 is a portion forming a vibrating surface on the outer peripheral side of the bobbin connecting portion 11, and forms a vibrating surface such as a side surface portion of a flange-shaped truncated cone.

The first radiating portion 12 has a protruding portion 13 projecting to the front surface side where the central axis Q passes. The protrusion 13 is a portion formed at the center position of the first radiation portion 12 having a concave curved surface on the front surface side, and two protrusions 13 define the outer shape thereof in the cross section including the central axis Q shown in FIG. Located at the intersection of arcs. Since the respective center positions S1 or S2 of the two arcs are arranged on the front side of the bobbin connecting portion 11 as shown in the figure, the first radiating portion 12 has a concave curved surface on the front side. The center positions S1 and S2 are arranged symmetrically with respect to the central axis Q, and the directing angle θ is set in the positive direction and the directing angle θ is set in the negative direction, respectively.

The radii r1 and r2 of the two arcs defining the concave curved surface on the front side of the first radiating portion 12 are set to equal values, and the curved surface of the first radiating portion 12 is axisymmetric with respect to the central axis Q. It has a shape. The radii r1 and r2 of the two arcs are larger than the inner diameter radius r11 that defines the inner diameter dimension of the bobbin connecting portion 11, respectively, and the inner diameter radius r11 so that the protrusion 13 projecting to the front surface side is firmly formed. It is better to set the value smaller than the inner diameter, which is twice the inner diameter. If at least the radii r1 and r2 of the two arcs are set in this range, a protrusion 13 projecting to the front surface side can be formed where the central axis Q passes. If the radii r1 and r2 of the two arcs are made smaller than the inner diameter radius r11 that defines the inner diameter dimension of the bobbin connecting portion 11, the two arcs do not intersect, so that the protrusion 13 protruding to the front surface side cannot be formed. Further, if the radii r1 and r2 of the two arcs are set to a value larger than the inner diameter diameter which is twice the inner diameter radius r11, the protrusion 13 protrudes too much toward the front surface side.

In this embodiment, r1 = r2 = about 15 mm and r11 = about 10 mm. As shown in FIG. 2, the radii r1 and r2 of the two arcs defining the front side concave curved surface of the first radiating portion 12 are the front surface side of the first radiating portion 12 from their respective center positions S1 or S2. Although it is a radial dimension to, it may be a radial dimension to the central portion of the thickness of the first radiating portion 12 or a radial dimension to the surface on the back surface side of the first radiating portion 12. Since the protrusion 13 is the central portion of the dust cap 10, in the case of this embodiment, the thickness of the protrusion 13 in the front-rear direction is formed to be thicker than the thickness of the other portions.

As a result, assuming that the direction in which the central axis Q is extended as it is is the on-axis front with a directing angle θ = 0 degrees, the first radiation unit 12 has a directing angle θ deviated from the on-axis front in the cross-sectional shape including the central axis Q. A vibrating surface having a concave curved surface on the front side is formed so as to be substantially orthogonal to the direction (for example, ± 30 degrees). That is, since the first radiation unit 12 is inclined from the front in the cross section, it is suitable for radiating sound waves in the direction of a wide directivity angle θ deviating from the front on the axis.

On the other hand, the second radiating portion 15 is a portion forming a vibrating surface on the outer peripheral side of the bobbin connecting portion 11, and the diaphragm connecting portion 14 on the outer peripheral side is a coil 4b of the voice coil 4 rather than the bobbin connecting portion 11. Is located on the back side, so that a vibrating surface such as the side surface of a bobbin-shaped conical base is formed and connected to the diaphragm 2 on the outer peripheral side. Therefore, the diaphragm connecting portion 14 connected to the diaphragm 2 is connected so as to be substantially orthogonal to the diaphragm portion near the inner diameter portion of the diaphragm 2 in the cross-sectional shape including the central axis Q.

As a result, similarly to the first radiation unit 12, the second radiation unit 15 is substantially orthogonal to the direction of the pointing angle θ (for example, ± 30 degrees) deviated from the front on the axis in the cross-sectional shape including the central axis Q. It forms a vibrating surface like the side surface of a rectangular cone. That is, since the first radiating portion 12 and the second radiating portion 15 are inclined from the front in the cross section, they are suitable for radiating sound waves in the direction of a wide directivity angle θ deviating from the front on the axis.

Since the first radiating portion 12 having the concave curved surface on the front surface side of the dust cap 10 is sharpened so that the protrusion 13 is formed at the center thereof, the rigidity of the protrusion 13 and its periphery is increased. With this dust cap 10, it is possible to suppress split vibration in which only the protrusion 13 which is the central apex vibrates. Further, since the diaphragm connecting portion 14 on the outer peripheral side of the second radiation portion 15 is connected so as to be substantially orthogonal to the vicinity of the root of the cone-shaped diaphragm 2, the cone-shaped diaphragm 2 and the voice coil 4 are connected. The rigidity of the vibration system as a whole including the bobbin 4a and the dust cap 10 is increased. Therefore, the electrokinetic speaker 1 including the dust cap 10 can raise the high frequency limit frequency due to the divided vibration to improve the sound pressure frequency characteristic in the ultra-high frequency range of 20 kHz to 40 kHz.

FIG. 3 is a graph showing the sound pressure frequency characteristics of the electrokinetic speaker 1 of this embodiment. Specifically, in FIG. 3, the horizontal axis is a frequency of 10 kHz to 50 kHz, and the vertical axis is a sound pressure level (SPL [dB]). The electrodynamic speaker 1 is a full-range electrodynamic speaker, but in the graph of FIG. 3, the frequency characteristics in the human audible frequency band having a frequency of 10 kHz or less are not shown and correspond to high resolution audio. It shows an ultra-high frequency range that exceeds the audible frequency band required for the speaker. The solid line of the graph is the sound pressure frequency characteristic in front of the axis at the directional angle θ = 0 degrees, and the broken line is the sound pressure frequency characteristic at the directional angle θ = 30 degrees.

In the case of this embodiment shown in the graph of FIG. 3, the sound pressure at a directing angle θ = 30 degrees is lower than the sound pressure in front of the axis at about 25 kHz or less, but the axis is at about 25 kHz or more. The difference from the sound pressure in the upper front is not so much. Since the electrokinetic speaker 1 provided with the dust cap 10 of this embodiment forms a strong vibration system with the diaphragm 2 and the voice coil 4, it realizes a wide reproduction frequency characteristic in which the high frequency limit frequency extends to about 40 kHz or more. ing. Further, since it is provided with a concave curved surface on the front surface side of the first radiating portion 12 and a curved surface of the second radiating portion 15 formed like a side surface portion of a truncated cone, the on-axis front surface and the directivity angle θ = 30 degrees. The difference in sound pressure frequency characteristics between 20 kHz and 40 kHz is relatively small. This means that it has a wide and preferable directivity, and shows desirable characteristics as an electrodynamic speaker corresponding to high resolution audio.

On the other hand, FIG. 4 is a graph showing the sound pressure frequency characteristics of the electrokinetic speaker 1a (not shown) of the comparative example. The electrokinetic speaker 1a of the comparative example is different in that the dust cap 100 of the comparative example (not shown) is provided in place of the dust cap 10 of the present embodiment. The dust cap 100 of the comparative example is different from the dust cap 10 of the present embodiment in that it does not have the second radiation unit 15, and has the same configuration as the others. Therefore, the dust cap 100 of the comparative example includes a bobbin connecting portion 11 connected to the end of the bobbin 4a around which the coil 4b is wound, and a first radiating portion 12 defined on the inner peripheral side of the bobbin connecting portion 11. It is common in that it has.

Also in the graph of FIG. 4 showing the case of the comparative example, the solid line is the sound pressure frequency characteristic in front of the axis at the directional angle θ = 0 degrees, and the broken line is the sound pressure frequency characteristic at the directional angle θ = 30 degrees. .. In the case of the dust cap 100 of the comparative example, the sound pressure at the directing angle θ = 30 degrees is lower than the sound pressure at the front on the axis at about 25 kHz or less, which is the same as in the case of this embodiment. However, it differs in that the difference from the sound pressure on the front of the axis is large even at about 25 kHz or higher.

Since the electrodynamic speaker 1a provided with the dust cap 100 of the comparative example has the rigidity of the dust cap 100 improved to some extent, it realizes a wide reproduction frequency characteristic in which the high frequency limit frequency extends to about 40 kHz or more on the front on the axis. .. However, since the curved surface of the second radiation portion 15 formed like the side surface portion of the truncated cone is not provided, the difference in sound pressure frequency characteristics of 20 kHz to 40 kHz is large between the front on the axis and the directivity angle θ = 30 degrees. Become. This means that the directivity is narrower than that of the electrokinetic speaker 1 of the present embodiment, and shows an undesired characteristic as an electrodynamic speaker corresponding to high resolution audio. Therefore, the electrokinetic speaker 1 provided with the dust cap 10 of the present embodiment is superior to the electrokinetic speaker 1a provided with the dust cap 100 of the comparative example in the acoustic radiation characteristics near the high frequency limit frequency. ..

In the above embodiment, the dust cap 10 is made of a paper material obtained by blending cellulose nanofibers with wood pulp and mixing them, but of course, a material similar to that of a diaphragm using another material having excellent acoustic radiation characteristics is used. You may use it. For example, the dust cap 10 may be formed by injection molding or the like using a resin material, or may be formed by a method such as press molding of a metal material.

Further, in the above embodiment, the concave curved surface on the front surface side of the first radiating portion 12 is formed by two arcs having the same radius r1 and r2 in the cross section including the central axis Q shown in FIG. 2, respectively. The arc may be replaced with a curve formed by connecting a plurality of arcs having different radii. Even if they are replaced with those curves, a protrusion 13 projecting to the front surface can be formed at a place where the central axis Q of the first radiation portion 12 passes, and the rigidity of that portion can be increased. Just do it.

Further, in the above embodiment, the curved surface of the second radiation portion 15 is a curved surface such as a side surface portion of a flange-shaped truncated cone, but the cross-sectional shape thereof may also be a straight line or a curved line including an arc. It suffices if the diaphragm connecting portion 14 is located on the back side where the coil 4b of the voice coil 4 is located rather than the bobbin connecting portion 11, and the sound wave is emitted in the direction of a wide pointing angle θ off the front on the axis. Anything that can form a vibration surface suitable for

The dust cap of the present invention is not limited to the full-range type electrodynamic speaker 1 as shown in the figure, but is a woofer which is an electrodynamic speaker having a large diaphragm area and excellent in low-pitched sound reproduction, or high-pitched sound reproduction. It may be used for either a tweeter, which is an electrodynamic speaker having an excellent diaphragm area and a small area, or a squawker, which is an electrodynamic speaker suitable for reproducing the midrange. Further, the electrodynamic speaker 1 provided with the dust cap of the present invention is not limited to home stereo reproduction or multi-channel surround reproduction, but can also be applied to in-vehicle audio equipment and sound reproduction equipment such as movie theaters. Is. Moreover, it can be applied not only to a large speaker but also to headphones, earphones and the like.

1 Dynamic speaker 2 Vibration plate 3 Edge 4 Voice coil 5 Damper 6 Frame 7 Terminal 8 Magnetic circuit 9 Magnetic gap 10 Dust cap 11 Bobbin connection part 12 1st radiation part 13 Protrusion part 14 Vibration plate connection part 15 2nd radiation part

Claims (4)

A bobbin connecting part that connects to the end of the bobbin around which the coil is wound,
The first radiating portion defined on the inner peripheral side of the bobbin connecting portion and
The second radiating portion defined on the outer peripheral side of the bobbin connecting portion and
A diaphragm connecting portion connected to the diaphragm on the outer peripheral side of the second radiation portion is provided.
In the cross section including the central axis Q of the bobbin, the diaphragm connecting portion is located on the back surface side where the coil is located with respect to the bobbin connecting portion and is connected to the diaphragm.
The outer shape of the first radiation part is
The center positions of at least two arcs defining the cross-sectional shape are arranged on the front side opposite to the back side of the bobbin connecting portion, respectively, and have a concave curved surface on the front side.
A protrusion protruding toward the front surface is formed at the intersection of the two arcs on the central axis Q, and the protrusion is formed.
It is symmetrical about the central axis Q and is symmetrical.
Formed separately from the diaphragm,
Dust cap. The radius of the arc that defines the outer shape of the first radiation portion is
Each is set to a value larger than the inner diameter radius that defines the inner diameter dimension of the bobbin connecting portion and smaller than the inner diameter diameter that is twice the inner diameter radius.
The dust cap according to claim 1. The dust cap according to claim 1 or 2,
A voice coil including the bobbin and the coil connected to the bobbin connecting portion of the dust cap,
A magnetic circuit having a magnetic gap in which the coil is arranged, and
At least including the diaphragm connecting portion of the dust cap and the diaphragm connected to the bobbin.
Electrodynamic speaker. The diaphragm has a cone-shaped diaphragm portion extending from an inner diameter portion defining a central hole and having an outer diameter portion located on the front surface side.
The diaphragm connecting portion of the dust cap is connected so as to be substantially orthogonal to the diaphragm portion.
The electrokinetic speaker according to claim 3.

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