Patent Description:
In a speaker described in <CIT>, a frame is fixed to an upper portion of a magnetic circuit and a vibration system including a diaphragm and a coil is supported by an edge and a damper so as to vibrate freely inside the frame. A holding member having a large heat-dissipation area is fixed to an upper surface of a center pole of the magnetic circuit and an amplifier is fixed on the holding member. This invention is an invention that, when the diaphragm vibrates with a large amplitude in a low-frequency band and an air volume is increased above the diaphragm, can increase the heat-dissipation effect and the cooling effect of the amplifier that is exposed to outside air above the diaphragm.

In an acoustic apparatus described in <CIT>, a driving-body cone and a driving motor structural body that vibrates the driving-body cone are provided at a frame member. An amplifier assembly is provided at a capacity portion disposed forward of the driving-body cone. The amplifier assembly has a heat sink and an amplifier cover that thermally contacts the heat sink and holds an amplifier. This invention is also an invention in which, when the driving-body cone vibrates with an audible-range frequency, air motion is produced at the capacity portion due to a pressure wave that becomes a sound wave, and heat is easily dissipated from the amplifier assembly.

The inventions described in <CIT> and <CIT> are inventions in which, when the diaphragm or the driving-body cone has vibrated, an airflow similar to a laminar flow is produced forward of the diaphragm or the driving-body cone, and the airflow similar to a laminar flow only reciprocates back and forth in a wide area. Since the amplifier is merely disposed by being exposed to air existing forward of the diaphragm or the driving-body cone, even if the airflow similar to a laminar flow acts upon the amplifier, air around the amplifier cannot be sufficiently mixed, and thus heat tends to be retained around the amplifier, as a result of which there is a limit to how high the heat-dissipation effect can be made.

<CIT> discloses an electronic device which may play audio signals through speakers. A speaker such as a subwoofer may be mounted in a device housing above the power supply so that airflow from the speaker cools the power supply. To enhance cooling, the control circuitry may supply inaudible signals to the speaker that enhance airflow produced by the speaker. The positioning of the power supply and subwoofer adjacent to one another within the device serves to provide cooling to power supply when needed, even in the absence of additional optional thermal management operations. Due to angled shapes or other airflow biasing shapes of airflow biasing structures, movement of the speaker causes a flow of air through the device that cools the internal components of device.

<CIT> discloses an omni-directional acoustic deflector which includes an acoustically reflective body having a substantially conical outer surface, and an inner surface opposite the outer surface which defines a region that is configured to be coupled to an electronic component such that heat is transferred from the electronic component to the outer surface of the reflective body.

<CIT> discloses an acoustic device having a heat producing device, such as an amplifier and a heat sink for transferring heat from the amplifier. The acoustic device has a cone having an inner surface, and a support structure defining a volume. The heat producing element and the heat sink are positioned in the volume.

An object of the present invention is to provide a speaker that is capable of increasing the heat-dissipation effect of a circuit part.

The invention relates to a speaker according to the appended claims. Embodiments are disclosed in the dependent claims.

According to an aspect, there is provided a speaker including a vibration part that includes a diaphragm and a voice coil, a magnetic circuit part that applies a magnetic field to the voice coil, and a supporting body that supports the vibration part and the magnetic circuit part. In the speaker, the supporting body includes a cover member that covers the vibration part from one of vibration directions of the vibration part, and a duct that causes a space between the vibration part and the cover member to communicate with outside space situated outward of the cover member. In addition, an air flow path where an interval between the vibration part and the cover member in the vibration directions is wider than an interval at another part in the space between the vibration part and the cover member is formed, and the air flow path communicates with an inside of the duct. Further, a circuit part provided on an outer side of the cover member and a heat sink that has at least a part thereof exposed in the air flow path are connected to each other to allow heat conduction.

The cover member is such that a part of a region thereof that covers the vibration part has a recessed portion recessed in a direction away from the vibration part, and an inside of the recessed portion functions as the air flow path.

According to an embodiment of the speaker of the present invention, for example, the duct is displaced from the central axis.

Alternatively, according to an embodiment of the speaker of the present invention, the duct is displaced from the central axis of the vibration part, and at least a part of the air flow path passes through the central axis.

Alternatively, according to an embodiment of the speaker of the present invention, the duct is provided on the central axis of the vibration part, and the air flow path extends toward the central axis from an outer peripheral side of the vibration part.

The diaphragm has a tapering portion, and the cover member includes a cover tapering portion that faces the tapering portion of the diaphragm and that is inclined in a same direction as the tapering portion of the diaphragm, and the interval at the air flow path in the vibration directions is wider than an interval between the vibration part and the cover tapering portion in the vibration directions.

According to an embodiment of the speaker of the present invention, it is preferable that the heat sink have a groove, and that the groove extend through the heat sink in a direction toward the duct in the air flow path.

According to an embodiment of the speaker of the present invention, the circuit part may have a circuit board fixed to an outer surface of the cover member, and an electronic element mounted on the circuit board, and the heat sink may be connected to the circuit part via an opening in the cover member.

The speaker according to aspects of the present invention includes a cover member that covers the diaphragm from one of the vibration directions of the vibration part. Therefore, an air flow path that communicates with the duct is formed in a closed space between the diaphragm and the cover member, and a heat sink is disposed in the air flow path. Since, when the vibration part vibrates, an airflow is produced in the air flow path, heat can be effectively dissipated from the heat sink that is positioned in the air flow path.

In a first embodiment to a fourth embodiment of the present invention described below, Y1-Y2 directions are vibration directions of a vibration part <NUM>. In each embodiment, the Y1 direction is a sound-producing direction in a forward direction, and the Y2 direction is a rearward direction. A speaker of each embodiment is used for being mounted on a vehicle. In an installation example of the speaker, the forward direction (Y1 direction), which is the sound-producing direction, is toward the inside of a compartment of a vehicle, and a duct <NUM> provided rearward is fixed to the body of the vehicle so as to communicate with outside space of the vehicle. In another installation example, the speaker is disposed in a space situated outside the compartment of the vehicle, such as an engine room or a trunk room, and the duct <NUM> is oriented toward the inside of the compartment of the vehicle. In this case, the Y2 direction becomes the sound-producing direction in the forward direction toward the inside of the compartment of the vehicle, and the Y1 direction becomes the rearward direction toward the outside of the vehicle.

In a speaker <NUM> of the first embodiment of the present invention shown in <FIG>, the illustrated downward direction is the sound-producing direction in the forward direction (Y1 direction), and the illustrated upward direction is the rearward direction (Y2 direction). Even in the second embodiment to the fourth embodiment, which are illustrated in a corresponding one of <FIG> and subsequent figures, the illustrated downward direction is the sound-producing direction in the forward direction (Y1 direction), and the illustrated upward direction is the rearward direction (Y2 direction).

The speaker <NUM> shown in <FIG> has a supporting body <NUM>. As shown in <FIG>, the supporting body <NUM> has a front frame <NUM> that is positioned on a forward side, a rear frame <NUM> that is positioned on a rearward side, a cover member <NUM> that is positioned rearward of the rear frame <NUM> and that is placed upon the rear frame <NUM>, and a duct <NUM> provided at the cover member <NUM>. The duct <NUM> is integrated with the cover member <NUM>. Alternatively, the duct <NUM> is formed separately from the cover member <NUM>, and is fixed to the cover member <NUM>. A diaphragm <NUM> is provided inside the speaker <NUM>. The diaphragm <NUM> is such that its planar shape projected from the front or the rear is a circular shape. The diaphragm <NUM> has a tapering portion whose diameter gradually increases in the forward direction (Y1 direction), which the sound-producing direction. The main parts, that is, the front frame <NUM>, the rear frame <NUM>, and the cover member <NUM> are such that their planar shapes projected from the front or the rear are circular shapes. Note that the diaphragm <NUM>, the front frame <NUM>, the rear frame <NUM>, and the cover member <NUM> may be such that their planar shapes projected from the front or the rear are elliptical shapes or oval shapes.

As shown in <FIG>, a plurality of openings 11a are formed in the front frame <NUM>, and sound pressure produced by vibration of the diaphragm <NUM> can be directed forward (Y1 direction) via the openings 11a. A plurality of openings 12a are also formed in the rear frame <NUM>. The cover member <NUM> covers, excluding an inside space of the duct <NUM>, the entire region of a space behind the vibration part <NUM> including the diaphragm <NUM> so as to close the entire region.

As shown in <FIG>, the vibration part <NUM> has the diaphragm <NUM>, an edge member <NUM>, a bobbin <NUM>, and a cap member <NUM>. Each figure showing a corresponding one of the embodiments shows a central axis O extending through the center of the vibration part <NUM> and extending in a front-rear direction (vibration direction of the vibration part <NUM>). The edge member <NUM> is made of an elastically deformable sheet material and is formed so that its cross section is curved in a semicircular shape. The edge member <NUM> is such that its planar shape when viewed from the front or rear is a ring shape, and its inner peripheral portion 4a is adhered to an outer peripheral edge 3a of the diaphragm <NUM>. An outer peripheral portion 4b of the edge member <NUM> is interposed between an outer peripheral portion of the front frame <NUM> and an outer peripheral portion of the rear frame <NUM>, and the outer peripheral portion of the front frame <NUM> and the outer peripheral portion of the rear frame <NUM> and an outer peripheral portion of the cover member <NUM> are fixed with, for example, screws. The bobbin <NUM> is provided on the central axis O of the speaker <NUM>, and an inner peripheral edge 3b of the diaphragm <NUM> is adhered and fixed to an outer peripheral surface of the bobbin <NUM>. A rearwardly (Y2 direction) facing opening of the bobbin <NUM> is covered by the cap member <NUM>.

Damper members <NUM> are provided inside the speaker <NUM>. Each damper member <NUM> is made of an elastically deformable sheet material, and has a cross section formed with a corrugated shape. Two damper members <NUM> are provided parallel to each other in the front-rear direction. An outer peripheral portion 7a of each damper member <NUM> is adhered and fixed to the rear frame <NUM>, and an inner peripheral portion 7b of each damper member <NUM> is adhered and fixed to the outer peripheral surface of the bobbin <NUM>. In the vibration part <NUM>, the diaphragm <NUM>, the bobbin <NUM>, and the cap member <NUM> are supported by the edge member <NUM>, which is a part of the vibration part <NUM>, and the damper members <NUM> so as to vibrate freely in the front-rear direction.

As shown in <FIG>, a voice coil <NUM> is wound around an outer periphery of a front (Y1 direction) end portion of the bobbin <NUM>. The voice coil <NUM> is also a part of the vibration part <NUM>. The voice coil <NUM> and a magnetic circuit part <NUM> constitute a magnetic driving part. The magnetic circuit part <NUM> has a front yoke <NUM>, a center pole <NUM>, and a rear yoke <NUM>. The front yoke <NUM>, the center pole <NUM>, and the rear yoke <NUM> are made of a magnetic material. A ring-shaped magnet <NUM> is interposed between the front yoke <NUM> and the rear yoke <NUM>. A magnetic gap is formed at a facing portion where an outer peripheral surface of the center pole <NUM> and an inner peripheral surface of the rear yoke <NUM> face each other, and the voice coil <NUM> is positioned in the magnetic gap. Due to a magnetic field that is produced from the magnet <NUM>, a magnetic flux that passes inside the magnetic gap crosses the voice coil <NUM>.

As shown in <FIG> and <FIG>, the cover member <NUM> is such that its ring-shaped region formed around the central axis O is a cover tapering portion 13a. As shown in <FIG>, the cover tapering portion 13a is inclined in the same direction as the tapering portion of the diaphragm <NUM>, and the tapering portion of the diaphragm <NUM> and the cover tapering portion 13a face each other substantially in parallel to each other. The cover member <NUM> is such that a region of its central portion surrounded by the cover tapering portion 13a is a protruding portion 13b that protrudes rearward. A recessed portion 13c that is recessed rearward (Y2 direction) in a direction away from the vibration part <NUM> is formed at a forwardly (Y1 direction) facing inner surface of the cover member <NUM>. The recessed portion 13c is formed along an arc locus formed around the central axis O at an outer periphery of the cover tapering portion 13a.

As shown in <FIG>, a space <NUM> is formed between the vibration part <NUM> and the cover member <NUM>. At the vibration part <NUM>, the edge member <NUM> is provided around an outer periphery of the diaphragm <NUM>, and the cap member <NUM> that covers the opening of the bobbin <NUM> is provided at a central portion of the diaphragm <NUM>. Therefore, the space <NUM> provided rearward (Y2 direction) of the vibration part <NUM> is provided apart from a space provided forward (Y1 direction) of the vibration part <NUM>. The inside space of the duct <NUM> communicates with the space <NUM>, and the space <NUM> is provided apart from outside space excluding the inside space of the duct <NUM>.

As shown in <FIG>, inside the space <NUM>, at a region where the recessed portion 13c is formed, an interval (interval in the vibration direction of the vibration part <NUM>) L1 in the front-rear direction between a rearwardly (Y2 direction) facing rear surface of the vibration part <NUM> and a forwardly (Y1 direction) facing front surface of the cover member <NUM> is wider than an interval in the front-rear direction at the other part in the space <NUM>. In the embodiment shown in <FIG>, the other part is a facing portion where the tapering portion of the diaphragm <NUM> and the cover tapering portion 13a face each other. The interval L1 in the front-rear direction at a portion where the recessed portion 13c is formed is wider than an interval (interval in the vibration direction of the vibration part <NUM>) L2 in the front-rear direction at the facing portion.

In the space <NUM> between the vibration part <NUM> and the cover member <NUM>, the region having the interval L1 and formed along an arc locus formed around the central axis O is an air flow path <NUM>. In the present specification, an inside space of the recessed portion 13c of the cover member <NUM> alone can be defined as the air flow path <NUM>. This is the definition of the air flow path in a narrow sense. The inside space of the recessed portion 13c, an inside space of the edge member <NUM> having a semicircular shape in cross section, and the space interposed between the recessed portion 13c and the edge member <NUM> from the front and rear (space having the interval L1) can be defined in their entirety as the air flow path <NUM>. This is the definition of the air flow path in a wide sense. Alternatively, a region in which the inside space of the edge member <NUM> is removed from the region having the interval L1 can be defined as the air flow path <NUM>. In a structure in which the cover member <NUM> does not have a recessed portion 13c, a region in which the inside space of the recessed portion 13c is removed from the region having the interval L1, that is, the inside space of the edge member <NUM> and a space that is formed continuously with a rear side of the inside space of the edge member <NUM> function as the air flow path <NUM>.

As shown in <FIG> and <FIG>, at a region having a constant radius from the central axis O, the air flow path <NUM> extends along an arc locus formed around the central axis O. The air flow path <NUM> communicates with the inside space of the duct <NUM>. By forming the air flow path <NUM> along the arc locus having a constant radius from the central axis O as the center, when the vibration part <NUM> vibrates back and forth, the viscous resistance of air that occurs due to the space <NUM> can evenly act upon the vibration part <NUM>.

As shown in <FIG>, an opening <NUM> is formed in the cover member <NUM> in the region where the recessed portion 13c is formed and at a position near the duct <NUM>. In the region where the opening <NUM> is formed, a circuit part <NUM> is mounted on a rearwardly facing outer surface of the cover member <NUM>. The circuit part <NUM> has a circuit board <NUM>, and electronic elements (electronic components) <NUM> are mounted on a rearwardly facing surface of the circuit board <NUM>. The circuit part <NUM> constitutes an amplifier, and a heating electronic element (heating electronic component) is included among the electronic elements <NUM>. The outer surface of the cover member <NUM>, where the circuit part <NUM> is mounted, is a flat surface, and the circuit part <NUM> can be stably mounted.

As shown in <FIG>, in an inside space situated forward of the recessed portion 13c, at least a part of a heat sink <NUM> is provided at a portion where the opening <NUM> is formed. The heat sink <NUM> is made of a metallic material having a high thermal conductivity, such as aluminum or an aluminum alloy. A heat-conducting part that contacts the heating electronic element is formed from, for example, a metallic layer and on a forwardly (Y1 direction) facing surface of the circuit board <NUM>. The heat sink <NUM> is connected to the heat-conducting part, and the heat sink <NUM> and the circuit part <NUM> are connected to each other to allow thermal conduction via the inside of the opening <NUM>. As shown in <FIG> and <FIG>, a plurality of grooves 33a are formed in the heat sink <NUM> so as to extend therethrough in a direction intersecting the front-rear directions (Y1-Y2 directions). Inside the recessed portion 13c, the grooves 33a extend through the heat sink <NUM> in a direction of flow of air in the air flow path <NUM>, that is, in a direction toward the duct <NUM>.

Next, an operation of the speaker <NUM> is described.

In a sound-producing operation, a drive current is applied to the voice coil <NUM> based on an audio signal that has been output from an audio amplifier. At the magnetic circuit part <NUM>, a drive magnetic flux circulates based on a magnetic field of the magnet <NUM>, and the drive magnetic flux crosses the voice coil <NUM> that is positioned in the magnetic gap. By an electromagnetic force that is excited by the drive magnetic flux that crosses the magnetic gap and the drive current of the voice coil <NUM>, the vibration part <NUM> including the diaphragm <NUM>, the edge member <NUM>, the bobbin <NUM>, and the cap member <NUM> vibrates in the front-rear direction. Due to primarily the vibration of the diaphragm <NUM> in the front-rear direction, sound pressure that is produced forward (Y1 direction) of the diaphragm <NUM> passes through the opening 11a of the front frame <NUM> and is applied to the inside of a compartment of a vehicle. Although air pressure having a phase that is opposite to that of the sound pressure is produced rearward (Y2 direction) of the diaphragm <NUM>, the air pressure is discharged to the outside via the inside space of the duct <NUM> from the space <NUM> between the vibration part <NUM> and the cover member <NUM>. Therefore, the sound pressure that is produced in the forward direction (Y1 direction) and the air pressure having a phase that is opposite to that of the sound pressure are suppressed from interfering with each other.

In the space <NUM> between the vibration part <NUM> and the cover member <NUM>, based on the vibration of the vibration part <NUM> in the front-rear direction, the air pressure changes and an airflow is produced due to the change in the air pressure. In the space <NUM>, the front-rear interval L2 at the facing portion where the tapering portion of the diaphragm <NUM> and the cover tapering portion 13a face each other is narrow, and the front-rear interval L1 at the air flow path <NUM> is wide. Therefore, due to a pressure change in a space having the interval L2 and provided between the tapering portions, the airflow easily concentrates at the air flow path <NUM> having the interval L1.

When the vibration part <NUM> moves rearward (Y2 direction), air that is compressed in the space having the narrow interval L2 and formed between the tapering portions flows into the air flow path <NUM>, an airflow is produced in the air flow path <NUM>, and the airflow is discharged to outside space from the duct <NUM>. When the vibration part <NUM> moves forward (Y1 direction), since the volume of the space having the interval L2 and formed between the tapering portions increases and the air pressure is reduced, air in outside space flows into the space having the interval L2 and formed between the tapering portions from the air flow path <NUM> via the inside of the duct <NUM>. Therefore, inside the space <NUM>, the airflow along the air flow path <NUM> inside the recessed portion 13c formed along an arc locus is easily produced, and the heat sink <NUM> that is positioned in the air flow path <NUM> is easily exposed to the airflow. Heat produced at the circuit part <NUM> is discharged into outside space situated rearward of the cover member <NUM>, and is transmitted to the airflow in the air flow path <NUM> via the heat sink <NUM> and is discharged to outside space via the inside space of the duct <NUM>. Inside the air flow path <NUM>, since the grooves 33a of the heat sink <NUM> extend in the direction of flow of air in the air flow path <NUM>, the effect of dissipating heat into the air flow path <NUM> from the heat sink <NUM> can be increased.

As shown in <FIG>, the cover member <NUM> is such that its recessed portion 13c is formed continuously with the cover tapering portion 13a, that is, the air flow path <NUM> that is formed continuously with a space situated forward of the cover tapering portion 13a is formed. The air flow path <NUM> is formed along an arc locus formed around the central axis O, and communicates with the inside of the duct <NUM> that is situated at an outer peripheral position displaced from the central axis O. In this structure, a flow easily concentrates in the air flow path <NUM> formed along the arc locus due to a pressure change in the space between the tapering portions, and the airflow moves to outside space via the inside space of the duct <NUM> that is positioned at an outer peripheral region. Since at least a part of the heat sink <NUM> is positioned in the air flow path <NUM> and near the duct <NUM>, heat is easily dissipated from the heat sink <NUM>.

In the second embodiment to the fourth embodiment, parts having the same functions as those of the first embodiment shown in <FIG>, are, even if they differ in, for example, their shapes, given the same reference numerals and are not described in detail below.

In a speaker <NUM> of the second embodiment shown in <FIG>, a supporting body <NUM> includes a front frame <NUM> and a cover member <NUM>, and does not include a rear frame <NUM>. An outer peripheral portion 4b of an edge member <NUM> that constitutes a vibration part <NUM> is fixed by being interposed between an outer peripheral portion of the front frame <NUM> and an outer peripheral portion of the cover member <NUM>. A diaphragm <NUM> that constitutes the vibration part <NUM> has a tapering portion whose diameter gradually increases rearward (Y2 direction), and an inclination direction of the tapering portion of the diaphragm <NUM> is opposite to that in the first embodiment in a front-rear direction. A damper member <NUM> is positioned forward (Y1 direction) of the diaphragm <NUM>. A cap member <NUM> that covers an opening situated rearward of a bobbin <NUM> has a dome shape whose protruding side faces rearward.

The cover member <NUM> has a dome-shaped protruding portion 13b formed at a central portion thereof, and protruding so as to match a rearward bulge of the cap member <NUM>. The cover member <NUM> has a cover tapering portion 13a that is formed continuously with an outer periphery of the protruding portion 13b and that tapers with respect to a central axis O as a center. The inclination direction of the cover tapering portion 13a is the same as the inclination direction of the tapering portion of the diaphragm <NUM>. A recessed portion 13c recessed rearward on an outer peripheral side of the cover tapering portion 13a is formed in a forwardly facing inner surface of the cover member <NUM>. Similarly to the first embodiment, the recessed portion 13c is formed continuously over substantially the entire periphery along an arc locus formed around the central axis O. A duct <NUM> is formed at the cover member <NUM> so as to be displaced from the central axis O, and the inside of the recessed portion 13c communicates with an inside space of the duct <NUM>.

As shown in <FIG>, in the speaker <NUM>, the recessed portion 13c of the cover member <NUM> is formed toward an inner peripheral side closer to the central axis O than a facing portion where the cover member <NUM> and the edge member <NUM> face each other, and, in a space <NUM>, a region where the recessed portion 13c and the diaphragm <NUM> face each other is an air flow path <NUM>. An interval of the air flow path <NUM> in a front-rear direction is L1. At a location closer to a central side than the recessed portion 13c, an interval L2 in the front-rear direction at a facing portion where a tapering portion of the diaphragm <NUM> and the cover tapering portion 13a face each other is narrow, and an interval in the front-rear direction at a facing portion where the cap member <NUM> and the dome-shaped protruding portion 13b face each other is substantially L2. Therefore, the interval L1 of the air flow path <NUM> in the front-rear direction is wider than the intervals at these regions in the space <NUM>.

A heat sink <NUM> is provided near the duct <NUM> inside the air flow path <NUM>, and a circuit part <NUM> mounted on an outer surface of the cover member <NUM> is connected to the heat sink <NUM> to allow heat conduction.

In the space <NUM> at a facing portion where the vibration part <NUM> and the cover member <NUM> face each other at the speaker <NUM> of the second embodiment, the interval L1 of the air flow path <NUM> in the front-rear direction is wide, and the interval L2 in the front-rear direction of the space <NUM> in the entire region situated inward of the air flow path <NUM> is narrow. Therefore, when the vibration part <NUM> vibrates back and forth, a pressure change at a portion, where the interval L2 is narrow, of a central portion where the cover tapering portion 13a and the protruding portion 13b are formed is increased, as a result of which an airflow having a high flow speed is formed from the air flow path <NUM> to the inside space of the duct <NUM>. Therefore, the effect of dissipating heat from the heat sink <NUM> can be increased.

The basic structure, as a speaker, of a speaker <NUM> of a third embodiment shown in <FIG> and <FIG> is the same as that of the speaker <NUM> of the second embodiment shown in <FIG>. A cover member <NUM> has a cover tapering portion 13a whose diameter gradually increases rearward, and the cover tapering portion 13a and a tapering portion of a diaphragm <NUM> face each other substantially in parallel to each other. In the cover member <NUM>, a recessed portion 13c is formed at a location closer than an edge member <NUM> to a central axis O, that is, at a location on the cover tapering portion 13a in a radial direction, and a central recessed portion 13d is further formed at a central portion. As shown in <FIG>, the recessed portion 13c is formed along an arc locus formed around the central axis O, and the central recessed portion 13d extends on the central axis O and linearly in a diameter direction. A duct <NUM> is displaced from the central axis O. In the cover member <NUM>, a protruding portion 13b is formed at a boundary portion between the cover tapering portion 13a and the central recessed portion 13d, and has a dome shape rounded rearward so as to match the shape of a cap member <NUM>.

As shown in <FIG>, a closed end portion 13e of the recessed portion 13c formed along the arc locus is disposed away from the duct <NUM>, and the recessed portion 13c does not directly communicate with the duct <NUM>. On a side opposite to where the duct <NUM> is provided with the central axis O in between, a midway portion of the arc-shaped recessed portion 13c and the central recessed portion 13d communicate with each other. The central recessed portion 13d communicates with an inside space of the duct <NUM>.

As shown in <FIG>, in a space <NUM> between a vibration part <NUM> and the cover member <NUM>, a facing interval L1 in a front-rear direction between the recessed portion 13c and the diaphragm <NUM> is wide, and a region where the recessed portion 13c and the diaphragm <NUM> face each other is an air flow path <NUM>. An inside space of the recessed portion 13c alone can be defined as the air flow path <NUM>. An interval L2 in the front-rear direction at a region that the cover tapering portion 13a, which is the other part in the space <NUM>, faces is narrower than the interval L1, and the distance in the front-rear direction at a region that the protruding portion 13b faces is also equal to the interval L2. An interval L3 in the front-rear direction between the central recessed portion 13d and the cap member <NUM>, which is a part of the vibration part <NUM>, is also wide, and a region where the central recessed portion 13d and the cap member <NUM> face each other is a central air flow path <NUM>. An inside space of the central recessed portion 13d alone can be defined as the central air flow path <NUM>. In the space <NUM>, the relationship between the intervals in the front-rear direction is L2 < L1 < L3.

A heat sink <NUM> is provided near the duct <NUM> inside the central air flow path <NUM>, and a circuit part <NUM> mounted on an outer surface of the cover member <NUM> is connected to the heat sink <NUM> to allow heat conduction.

Even in the speaker <NUM> of the third embodiment, when the vibration part <NUM> vibrates back and forth, in the space <NUM> between the vibration part <NUM> and the cover member <NUM>, a pressure change at a portion where the cover tapering portion 13a and the protruding portion 13b are formed and where the interval L2 is narrow is increased, as a result of which an airflow concentrates inside the air flow path <NUM> and inside the central air flow path <NUM>, where the intervals in the front-rear direction are wide. As shown in <FIG>, on an outer peripheral side of the recessed portion 13c, due to an airflow (ii) that is produced by a pressure change at a location between the tapering portion of the diaphragm <NUM> and the cover tapering portion 13a, primarily, an airflow in the air flow path <NUM> extending along a circumferential locus is accelerated. On an inner peripheral side of the recessed portion 13c, due to an airflow (i) that is produced by a pressure change at a location between the tapering portion of the diaphragm <NUM> and the cover tapering portion 13a, an airflow in the air flow path <NUM> and the central air flow path <NUM>, each extending along a circumferential locus, is accelerated.

Further, the airflow in the air flow path <NUM> that does not directly communicate with the duct <NUM> and that is formed along the arc locus accelerates the airflow in the central air flow path <NUM>, and the airflow having a relatively high speed in the central air flow path <NUM> increases the effect of dissipating heat from the heat sink <NUM>.

The basic structure, as a speaker, of a speaker <NUM> of a fourth embodiment shown in <FIG> and <FIG> is the same as that of the speaker <NUM> of the third embodiment shown in <FIG> and <FIG>. A cover member <NUM> of the speaker <NUM> of the fourth embodiment has a recessed portion 13c along an arc locus and around an outer peripheral portion of a cover tapering portion 13a. A duct <NUM> has a central portion including a central axis O of the cover member <NUM>. A linear recessed portion 13f is formed between the recessed portion 13c and the duct <NUM>.

In a space <NUM> between a vibration part <NUM> and the cover member <NUM>, at a region of an outer peripheral portion where the recessed portion 13c is formed, an interval L1 between the vibration part <NUM> and the cover member <NUM> in a front-rear direction is wide, and an inside space of the recessed portion 13c or a space where the recessed portion 13c and the vibration part <NUM> face each other is an air flow path <NUM> along an arc locus. At a region where the linear recessed portion 13f is formed, an interval L4 between a diaphragm <NUM> and the cover member <NUM> in the front-rear direction is wide, and an inside space of the linear recessed portion 13f or a space at a facing portion where the linear recessed portion 13f and the diaphragm <NUM> face each other is a linear air flow path <NUM>. The linear air flow path <NUM> extends toward a central portion from an outer peripheral side. The relationship between the intervals L1 and L4 and an interval L2 in the front-rear direction at a region where the cover tapering portion 13a is provided is L2 < L1 < L4.

In the speaker <NUM> of the fourth embodiment, when the vibration part <NUM> vibrates back and forth, in the space <NUM> between the vibration part <NUM> and the cover member <NUM>, a pressure change at a portion where the cover tapering portion 13a and a protruding portion 13b are formed and where the interval L2 is narrow is increased, as a result of which the speeds of airflows inside the air flow path <NUM> and the linear air flow path <NUM>, each of whose interval in the front-rear direction is wide, are increased. In addition, the airflow in the air flow path <NUM> along the arc locus accelerates the airflow in the linear air flow path <NUM>, as a result of which air enters and exits between the space <NUM> and outside space via an inside space of the duct <NUM>.

Since a circuit part <NUM> is mounted on an outer side of the linear recessed portion 13f and a heat sink <NUM> is provided at the linear air flow path <NUM>, the effect of dissipating heat from the heat sink <NUM> by the airflow in the linear air flow path <NUM> is increased.

Claim 1:
A speaker (<NUM>, <NUM>, <NUM>, <NUM>) comprising:
a vibration part (<NUM>) that includes a diaphragm (<NUM>) having a tapering portion and a voice coil (<NUM>);
a magnetic circuit part (<NUM>) configured to apply a magnetic field to the voice coil; and
a supporting body (<NUM>) configured to support the vibration part and the magnetic circuit part,
wherein the supporting body (<NUM>) includes a cover member (<NUM>) configured to cover the vibration part (<NUM>) from one of vibration directions of the vibration part and including a cover tapering portion (13a) that faces the tapering portion of the diaphragm (<NUM>) and that is inclined in a same direction as the tapering portion of the diaphragm (<NUM>), and a duct (<NUM>) configured to cause a space between the vibration part (<NUM>) and the cover member (<NUM>) to communicate with outside space situated outward of the cover member,
wherein an air flow path (<NUM>, <NUM>, <NUM>) is formed which communicates with an inside of the duct (<NUM>), wherein the cover member (<NUM>) is such that a part of a region thereof configured to cover the vibration part (<NUM>) has a recessed portion (13c) recessed in a direction away from the vibration part (<NUM>) and an inside of the recessed portion (13c) is configured to function as the air flow path (<NUM>) where an interval (L1) between the vibration part (<NUM>) and the cover member (<NUM>) in the vibration directions is wider than an interval (L2) between the vibration part (<NUM>) and the cover tapering portion (13a) in the vibration directions, and
wherein a circuit part (<NUM>) provided on an outer side of the cover member (<NUM>) and a heat sink (<NUM>) that has at least a part thereof exposed in the air flow path are connected to each other to allow heat conduction;
characterised in that
the air flow path (<NUM>) is formed along an arc locus formed around a central axis (O) of the vibration part.