JP2018160724A - Dust cap and electrokinetic speaker using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dust cap realizing an electrokinetic speaker excellent in acoustic radiation characteristics near the high frequency-band limit frequency.SOLUTION: A dust cap 10 includes a bobbin coupling part 11 coupling with the end of a bobbin around which a coil is wound, a first radiation part 12 defined on the inner peripheral side of the bobbin coupling part 11, a second radiation part 15 defined on the outer peripheral side of the bobbin coupling part 11, and a diaphragm coupling part 14 coupling with a diaphragm 2 on the outer peripheral side of the second radiation part 15. In the profile including the medial axis of the bobbin, the diaphragm coupling part 14 is coupled with the diaphragm 2 at a position closer to the back side, where the coil is located, than the bobbin coupling part 11. Outer shape of first radiation part 12 has a front side concave surface, where the center positions of at least two circular arcs defining the profile are located closer to the front side, opposite to the back side, than the bobbin coupling part 11, and a protrusion 13 protruding to the front side is formed at the intersection point of the two circular arcs on the medial axis Q.SELECTED DRAWING: Figure 2

Description

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

  In an electrodynamic speaker that reproduces sound, an audio signal current is supplied to a coil of a voice coil connected to a diaphragm. Since the coil is arranged in the magnetic gap of the magnetic circuit, the voice coil and the diaphragm are vibrated by a 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 general electrodynamic speakers, a voice coil is formed by winding a coil around a substantially cylindrical bobbin, and the inner diameter portion of the 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 abnormal noise may occur. 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 a portion where the voice coil of the diaphragm is connected to prevent malfunction. The dust cap is generally required for an electrodynamic speaker manufactured using a voice coil holder which is a manufacturing jig for determining the position of the voice coil in the magnetic gap. The dust cap is sometimes called a 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 that it has excellent sound radiation characteristics like the diaphragm. It is hoped that. For example, the dust cap is formed of a material that is light and has the same internal loss as the diaphragm, and the shape of the dust cap is also designed to increase the rigidity so that the divided vibration is reduced. Particularly in the vicinity of the high frequency limit of the reproduction frequency band of the electrodynamic speaker, the vibration characteristics and acoustic radiation characteristics of the dust cap have a great influence on the sound pressure frequency characteristics of the electrodynamic speaker. This is because, when the cone-shaped diaphragm is divided and vibrated at a high frequency limit fh or higher, only the periphery of the inner diameter to which the voice coil is attached vibrates greatly, and the dust cap attached in the vicinity vibrates.

  Various types of electrodynamic loudspeakers have been proposed in connection with the shape of the dust cap and the connection between the diaphragm or the voice coil bobbin. 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 in the opposite direction. An eccentric cone diaphragm having a second diaphragm defined, a bobbin attached to the voice coil attachment part, a voice coil having a coil, and a dust cap attached to an end of the bobbin of the voice coil. There is an electrodynamic speaker (Patent Document 1).

  Also, for example, a speaker having a diaphragm and a dust cap fixed to the diaphragm, the dust cap being discontinuous in the cross-sectional shape on the surface including the central axis, inside the fixed portion with the diaphragm. There exists a speaker which has (patent document 2). A magnetic circuit; a frame joined to the magnetic circuit; a voice coil inserted into a magnetic gap of the magnetic circuit; a damper having an inner periphery coupled to the voice coil and an outer periphery coupled to the frame; Is connected to the voice coil, and the speaker is connected to the diaphragm whose outer periphery is directly or indirectly connected to the frame and the center cap connected to the voice coil. The center cap is substantially perpendicular to the outer periphery. There is a speaker that has a cylindrical portion that extends to the inner diameter of the voice coil, and that has an inner diameter set to fit with at least the outer diameter of the upper end of the voice coil. (Patent Document 3).

  In recent audio equipment, “high resolution (or high resolution)” that “exceeds CD (compact disc) specifications” has attracted attention. Specifically, the Japan Audio Association defines the definition and operation of logos for high-resolution audio compatible devices. Among them, as stated in “Speaker / Headphone High Frequency Reproduction Performance: 40kHz or higher”, the high resolution electrodynamic speaker is limited by the high frequency range of human audible frequency band. A sound pressure frequency characteristic far exceeding a certain 20 kHz is required. It is preferable that the sound pressure frequency characteristic is not only satisfied by the measured value at 0 degrees on the front axis of the electrodynamic speaker, but also by satisfying the directivity 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 the longer wavelength, and the smaller the diaphragm area, the better the sound reproduction in the high frequency range with the shorter wavelength. Therefore, a full-range electrodynamic speaker that attempts to reproduce 20 Hz to 20 kHz, which is an extremely wide audible frequency band for humans, is often provided with a cone-shaped diaphragm having a certain large diaphragm area. There is a problem that it is very difficult to design the limit of the high frequency reproduction frequency band to be 20 kHz or more. In addition to the existence of the high-frequency limit frequency fh at which the cone-shaped diaphragm divides and vibrates, the high frequency band in which the wavelength is relatively short with respect to the diaphragm area has a sharp directional characteristic on the front side, and the directivity angle When becomes wider, the reproduction sound pressure level suddenly decreases.

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

JP 2010-109665 A JP 2000-308180 A JP 2005-269064 A

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

  The dust cap of the present invention is defined on a bobbin connecting portion connected to an end portion of a bobbin around which a coil is wound, a first radiating portion defined on the inner peripheral side of the bobbin connecting portion, and an outer peripheral side of the bobbin connecting portion. And a diaphragm coupling portion coupled to the diaphragm on the outer peripheral side of the second radiation portion, and in the cross section including the central axis Q of the bobbin, the diaphragm coupling portion is more than the bobbin coupling portion. Is located on the back side where the coil is located and is connected to the diaphragm, and the outer shape of the first radiating portion is such that the center position of at least two arcs defining the cross-sectional shape is the back side from the bobbin connecting portion. Protruding portions that are disposed on the front side opposite to each other, have a concave curved surface on the front side, and project toward the front side at the intersection of two arcs on the central axis Q are formed.

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

  Preferably, the electrodynamic speaker of the present invention includes the dust cap, a voice coil including a bobbin and a coil connected to a bobbin connecting portion of the dust cap, and a magnetic circuit having a magnetic gap in which the coil is disposed. And at least a diaphragm connecting portion of the dust cap and a diaphragm connected to the bobbin.

  Preferably, in the electrodynamic speaker according to the present invention, the diaphragm has a cone-shaped diaphragm portion that extends from an inner diameter portion that defines the center hole and an outer diameter portion is located on the front side, The diaphragm coupling portion of the cap is coupled so as to be substantially orthogonal to the diaphragm portion.

  The operation of the present invention will be described below.

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

  In the cross section including the central axis Q of the bobbin, the dust cap is connected to the diaphragm such that the diaphragm connecting portion is located on the back side where the coil is positioned with respect to the bobbin connecting portion. Therefore, the outer shape of the second radiating part is formed like the side part of the truncated cone. In addition, the outer shape of the first radiating portion is such that the center position of at least two arcs defining the cross-sectional shape is disposed on the front side opposite to the back side from the bobbin connecting portion, so that the front side is concave. It comes to have a curved surface. And the 1st radiation part forms the projection part projected to the front side at the intersection of two circular arcs on central axis Q in a section.

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

  Further, the dust cap has a wide directivity angle (for example, a curved surface of the first radiating portion on the front side and a curved surface of the second radiating portion formed like a side surface portion of the truncated cone deviating from the axial front. The angle is inclined from the front in the cross section so as to be suitable for emitting sound waves in the direction of ± 30 degrees. The area of the vibrating dust cap is increased by adding the area of the second radiating portion to the first radiating portion. Therefore, it can be improved as compared with the prior art so that the difference between the front characteristic and the directivity of the high sound range including the super high frequency range of 20 kHz to 40 kHz is reduced.

  In particular, when the diaphragm has a cone-shaped diaphragm part that extends from the inner diameter part that defines the center hole and the outer diameter part is located on the front side, an electrodynamic speaker suitable for the full-range type is realized. it can. The diaphragm coupling portion coupled to the diaphragm on the outer peripheral side of the second radiating portion of the dust cap is coupled 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 voice coil bobbin, and the dust cap is increased, the high frequency limit frequency due to the divided vibration is further increased, and the super high frequency range of 20 kHz to 40 kHz. The sound pressure frequency characteristics at can be improved.

  Even if the dust cap of the present invention is a full range type, it is possible to realize an electrodynamic speaker excellent in acoustic radiation characteristics in the vicinity of the high frequency limit frequency.

It is the front view and sectional drawing which show the specific structure of the electrodynamic speaker which concerns on one Embodiment of this invention. It is a partial expanded 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 electrodynamic speaker of a present Example. It is a graph which shows the sound pressure frequency characteristic of the electrodynamic type speaker of a comparative example.

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

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

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

  The diaphragm 2 has a cone-shaped diaphragm portion that extends from an inner diameter portion that defines the center hole and has an outer diameter portion located on the front side. In the following description, the direction in which the diaphragm 2 in FIGS. 1 and 2 is exposed is referred to as the front side, and the direction in which the magnetic circuit 8 in FIG. The diaphragm 2 of the present embodiment is a diaphragm made of a paper material obtained by blending cellulose nanofibers with wood pulp and mixing them. The diaphragm 2 has a structure in which the fibers are densely and firmly bonded to each other by blending cellulose nanofibers. As a result, a speaker diaphragm having an excellent Young's modulus and a wide reproduction frequency band can be obtained. .

  The outer diameter portion of the diaphragm 2 is supported by a relatively flexible edge 3 so as to vibrate. The edge 3 of the present embodiment is a roll edge whose upper surface has a convex section. The edge 3 has an inner peripheral connecting portion formed on the inner peripheral side of the movable portion, and an outer peripheral connecting portion 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 bonded and fixed to the outer diameter portion of the diaphragm 2, and the outer peripheral connecting portion on the outer peripheral side is bonded and fixed to the frame 6.

  The diaphragm 2 is connected with a substantially cylindrical bobbin 4a of the voice coil 4 fitted in the center hole of the inner diameter portion thereof. The bobbin 4a of the voice coil 4 is formed by, for example, forming a foil material having a predetermined thickness into a substantially cylindrical shape, the coil 4b is wound around the lower end portion thereof, and the outer curved surface where the coil 4b is not wound is reinforced. Paper is wound and formed into a cylindrical shape as a whole. A tinsel wire (not shown) is soldered and fixed to the voice coil 4 so that the other end side of the tinsel wire is electrically connected to a terminal 7 fixed to the frame 6. A voice signal current is supplied to the coil 4b of the voice coil 4 via the terminal 7 and the tinsel wire.

  Further, an inner diameter end of the damper 5 is 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 bonded and fixed to the damper fixing portion of the frame 6. The damper 5 may be an annular corrugation damper that is formed by impregnating a resin such as phenol resin with a woven fabric of flexible fibers as a base material, and is formed of other materials. Also good. 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 is an iron plate frame press-molded in a basket shape, and as described above, the outer peripheral connection 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 connected to the frame 6 at the end on the back side. The frame 6 may be an aluminum die-cast frame formed in a basket shape or a resin frame formed of resin.

  The magnetic circuit 8 includes an annular top plate fixed to the frame 6, a pole having a center pole and a flat under plate, and an annular magnet, and is arranged between the top plate and the pole. A circular magnetic gap 9 having a uniform width is formed. The magnetic gap 9 is supported and arranged by the edge 3 and the damper 5 so that the coil 4b of the voice coil 4 can vibrate without contacting the magnetic circuit 8. As long as the magnetic circuit 8 has a predetermined magnetic gap 9 corresponding to the voice coil 4, the magnetic circuit 8 is not limited to the outer magnetic type as in the present embodiment, and other magnetic circuit configurations such as an inner magnetic type are adopted. Also good.

  The electrodynamic speaker 1 includes a dust cap 10. Similar to the diaphragm 2, the dust cap 10 is a dust cap that is made of a paper material obtained by blending cellulose nanofibers with wood pulp and mixing them, and is excellent in 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 4 a of the voice coil 4.

  The dust cap 10 includes 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 first defined on the outer peripheral side of the bobbin connecting portion 11. 2 radiating section 15, and diaphragm connecting section 14 coupled to diaphragm 2 on the outer peripheral side of second radiating section 15. The bobbin connecting portion 11 is an annular portion defined by the inner diameter radius r11, and is a portion that is fitted and connected so that the end of the bobbin 4a of the voice coil 4 is within the inner diameter side. The 1st radiation | emission part 12 is a part which forms the vibration surface of the inner peripheral side of the bobbin connection part 11, Comprising: The projection part 13 mentioned later is included. Moreover, the 2nd radiation | emission part 15 is a part which forms the vibration surface of the outer peripheral side of the bobbin connection part 11, Comprising: A vibration surface like the side part of a bowl-shaped truncated cone is formed.

  The 1st radiation | emission part 12 has the projection part 13 which protrudes to the front side where the central axis Q passes. The projecting portion 13 is a portion formed at the center position of the first radiating portion 12 having a concave curved surface on the front side, and in a cross section including the central axis Q shown in FIG. Located at the intersection of arcs. Since the 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 drawing, the first radiating portion 12 has a concave curved surface on the front side. The center position S1 or S2 has an axially symmetrical arrangement relationship with respect to the center axis Q, and the directivity angle θ is set to a positive direction and the directivity angle θ is set to a negative direction, respectively.

  The radii r1 and r2 of the two arcs defining the front-side concave curved surface of the first radiating portion 12 are set to be 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 radius r11 that defines the inner diameter of the bobbin connecting portion 11 so that the projection 13 protruding to the front side is firmly formed, and the inner radius r11 It is good to set it to a 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 within this range, the protruding portion 13 protruding to the front side can be formed where the central axis Q passes. If the radii r1 and r2 of the two arcs are smaller than the inner radius r11 that defines the inner diameter of the bobbin connecting portion 11, the two arcs do not intersect with each other, so that the protruding portion 13 protruding to the front 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 that is twice the inner radius r11, the protrusion 13 protrudes too far to the front 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-side surfaces of the first radiating portion 12 from the respective center positions S1 or S2. However, 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 back surface of the first radiating portion 12. Since the protruding portion 13 is the central portion of the dust cap 10, in the present embodiment, the thickness of the protruding portion 13 in the front-rear direction is larger than the thickness of the other portions.

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

  On the other hand, the second radiating portion 15 is a portion that forms a vibration 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 4 b of the voice coil 4 than the bobbin connecting portion 11. Therefore, a vibration surface such as a side surface portion of a bowl-shaped truncated cone is formed and connected to the diaphragm 2 on the outer peripheral side. Therefore, the diaphragm coupling portion 14 coupled to the diaphragm 2 is coupled so as to be substantially orthogonal to the diaphragm portion in the vicinity of the inner diameter portion of the diaphragm 2 in the cross-sectional shape including the central axis Q.

  As a result, like the first radiating portion 12, the second radiating portion 15 is substantially orthogonal to the direction of the directivity angle θ (eg, ± 30 degrees) deviated from the axial front in the cross-sectional shape including the central axis Q. A vibration surface such as a side surface portion of a bowl-shaped truncated cone is formed. That is, since the first radiating section 12 and the second radiating section 15 are inclined at the angle from the front in the cross section, the first radiating section 12 and the second radiating section 15 are suitable for radiating sound waves in the direction of a wide directivity angle θ deviated from the axial front.

  Since the first radiating portion 12 having a 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 the periphery thereof is increased. In the dust cap 10, it is possible to suppress the divided vibration in which only the protrusion 13 that is the central vertex vibrates. Further, since the diaphragm connecting portion 14 on the outer peripheral side of the second radiating 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 entire vibration system including the bobbin 4a and the dust cap 10 is increased. Therefore, the electrodynamic speaker 1 including the dust cap 10 can improve the sound pressure frequency characteristic in the ultra high frequency range of 20 kHz to 40 kHz by further increasing the high frequency limit frequency due to the divided vibration.

  FIG. 3 is a graph showing sound pressure frequency characteristics of the electrodynamic speaker 1 of the present embodiment. Specifically, in FIG. 3, the horizontal axis is the frequency of 10 kHz to 50 kHz, and the vertical axis is the 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 with a frequency of 10 kHz or less are not shown, and the electrodynamic speaker 1 corresponds to high resolution audio. This indicates a super high frequency range that exceeds the audible frequency band required for this. The solid line in the graph is the sound pressure frequency characteristic at the front on the axis at the directivity angle θ = 0 degrees, and the broken line is the sound pressure frequency characteristic at the directivity angle θ = 30 degrees.

  In the case of the present embodiment shown in the graph of FIG. 3, the sound pressure at the directivity angle θ = 30 degrees is lower than the sound pressure at the front on the axis at about 25 kHz or less, but the axis at about 25 kHz or more. There is not much difference with the sound pressure at the front. Since the electrodynamic speaker 1 having 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. Moreover, since it comprises the concave curved surface on the front side of the first radiating portion 12 and the curved surface of the second radiating portion 15 formed like the side surface portion of the truncated cone, the axial front and the directivity angle θ = 30 degrees The difference in the sound pressure frequency characteristics of 20 kHz to 40 kHz is relatively small. This means that it has wide and preferable directivity characteristics, 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 electrodynamic speaker 1a (not shown) of the comparative example. The electrodynamic speaker 1a of the comparative example is different in that it includes a dust cap 100 (not shown) of the comparative example instead 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 the second radiating portion 15 is not provided, and the other components are the same. Therefore, the dust cap 100 of the comparative example includes a bobbin connecting portion 11 connected to an end portion of the bobbin 4a around which the coil 4b is wound, a first radiating portion 12 defined on the inner peripheral side of the bobbin connecting portion 11, It is common to have

  Also in the graph of FIG. 4 showing the case of the comparative example, the solid line is the sound pressure frequency characteristic at the front on the axis with the directivity angle θ = 0 degrees, and the broken line is the sound pressure frequency characteristic at the directivity angle θ = 30 degrees. . In the case of the dust cap 100 of the comparative example, the sound pressure at the directivity angle θ = 30 degrees is lower than the sound pressure at the front on the axis below about 25 kHz, as in the present embodiment. However, even at about 25 kHz or higher, there is a difference in that the difference from the sound pressure on the axial front is large.

  Since the rigidity of the dust cap 100 is improved to some extent, the electrodynamic speaker 1a provided with the dust cap 100 of the comparative example realizes a wide reproduction frequency characteristic in which the high-frequency limit frequency extends to about 40 kHz or more on the axial front. . However, since there is no curved surface of the second radiating portion 15 formed like the side portion of the truncated cone, there is a large difference in the sound pressure frequency characteristics of 20 kHz to 40 kHz between the axial front and the directivity angle θ = 30 degrees. Become. This means that the directivity characteristic is narrower than that in the case of the electrodynamic speaker 1 of the present embodiment, which is undesirable for an electrodynamic speaker corresponding to high resolution audio. Therefore, the electrodynamic speaker 1 provided with the dust cap 10 of the present embodiment is superior in acoustic radiation characteristics near the high-frequency limit frequency than the electrodynamic speaker 1a provided with the dust cap 100 of the comparative example. .

  In the above embodiment, the dust cap 10 is made of a paper material obtained by mixing and mixing cellulose nanofibers with wood pulp. Of course, the same material as the diaphragm using other materials having excellent acoustic radiation characteristics is used. It may be used. For example, the dust cap 10 may be formed by injection molding using a resin material, or may be formed by a method such as press molding a metal material.

  Further, in the above embodiment, the concave curved surface on the front side of the first radiating portion 12 is formed by two circular arcs having the same radii r1 and r2 in the cross section including the central axis Q illustrated in FIG. The arc may be replaced with a curve formed by connecting arcs having different radii. Even if these curves are replaced, it is possible to form the protruding portion 13 protruding to the front side where the central axis Q of the first radiating portion 12 passes, and to increase the rigidity of that portion. That's fine.

  Moreover, in the said Example, although the curved surface of the 2nd radiation | emission part 15 is a curved surface like the side part of a bowl-shaped truncated cone, the cross-sectional shape may be a curve containing a straight line or a circular arc. The diaphragm connecting portion 14 only needs to be positioned on the back side where the coil 4b of the voice coil 4 is positioned with respect to the bobbin connecting portion 11, and radiates sound waves in the direction of a wide directivity angle θ off the axial front. Any material can be used as long as it can form a vibration surface suitable for the above.

  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 that is an electrodynamic type speaker having a large diaphragm area that is excellent for low-frequency sound reproduction, or high-frequency sound reproduction. It may be adopted for either a tweeter that is an electrodynamic speaker having a small diaphragm area and a squawker that is an electrodynamic speaker suitable for reproduction in the middle range. In addition, the electrodynamic speaker 1 having the dust cap of the present invention is not limited to home stereo reproduction or multi-channel surround reproduction, and can be applied to in-vehicle audio equipment and sound reproduction equipment such as a movie theater. It is. Further, the present invention can be applied not only to large speakers but also to headphones, earphones, and the like.

DESCRIPTION OF SYMBOLS 1 Electrodynamic type speaker 2 Diaphragm 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 | emission part 13 Projection part 14 Diaphragm connection part 15 2nd radiation | emission part

Claims (4)

A bobbin connecting portion connected to the end of the bobbin around which the coil is wound, a first radiating portion defined on the inner peripheral side of the bobbin connecting portion, and a second radiation defined on the outer peripheral side of the bobbin connecting portion. And a diaphragm coupling part coupled to the diaphragm on the outer peripheral side of the second radiation part,
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 with respect to the bobbin connecting portion and is connected to the diaphragm,
The outer shape of the first radiating portion is such that the center positions of at least two arcs defining the cross-sectional shape are respectively disposed on the front side opposite to the back side from the bobbin connecting portion, and are concave on the front side. Forming a protrusion having a curved surface and projecting toward the front surface at the intersection of the two arcs on the central axis Q;
Dust cap. The radius of the arc that defines the outer shape of the first radiating portion is set to a value that is larger than the inner radius that defines the inner diameter of the bobbin connecting portion and smaller than the inner diameter that is twice the inner radius. Being
The dust cap according to claim 1. The dust cap according to claim 1, the bobbin coupled to the bobbin coupling portion of the dust cap and a voice coil including the coil, a magnetic circuit having a magnetic gap in which the coil is disposed, Including at least the diaphragm connecting portion of the dust cap and the diaphragm connected to the bobbin,
Electrodynamic type speaker. The diaphragm has a cone-shaped diaphragm part extending from an inner diameter part defining a central hole and an outer diameter part located on the front side, and the diaphragm coupling part of the dust cap Connect so as to be substantially orthogonal to the plate part,
The electrodynamic speaker according to claim 3.