Information
-
Patent Grant
-
6654478
-
Patent Number
6,654,478
-
Date Filed
Wednesday, December 12, 200122 years ago
-
Date Issued
Tuesday, November 25, 200320 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 381 396
- 381 412
- 381 431
- 381 407
- 381 FOR 159
- 340 3881
- 340 3911
- 340 3961
-
International Classifications
-
Abstract
A pole piece 31 is placed on a lower case 21. A pole piece 31 has a core 32 and a base 33. The bobbin portion 24 extends from the lower case 21 toward the internal space of a case 1 so as to surround the outer periphery of the core 32. The bobbin portion 24 is divided into a plurality of portions along the circumferential direction of the core 32. The bobbin portion 24 has basal parts 26 and elongated parts 27. The pole piece 31 is pressed from the above of the lower case 21 in a state where the bobbin portion 24 is passed through holes 35 of the base 33, to be positioned on the outer periphery of the core 32, so that the pole piece is fitted and placed into the lower case 21. A coil 41 is configured by winding a conductor wire 42 around the elongated parts 27 of the bobbin portion 24.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electroacoustic transducer which transduces an electrical signal into a sound.
2. Description of the Related Art
JP-A-8-6558 discloses an electroacoustic transducer which comprises a case in which a pole piece is mounted. The pole piece comprises a base and a core fixed integrally to each other. A coil is placed on the side of the outer periphery of the core. A magnet is placed around the coil with a gap formed therebetween. The coil is placed by directly winding a conductor wire around the core, or by mounting a prewound coil to the core.
However, the following problems arise in the electroacoustic transducer during a step of placing the coil. When the conductor wire is directly wound around the core, there is a possibility that the conductor wire (insulating layer thereof) is damaged by the core which is made of a metal. Also, when a prewound coil is attached to the core, there is a possibility that the core rubs against the conductive wire, damaging the wire, particularly the insulating layer thereof. When the conductor wire (insulating layer thereof) is damaged in this way, the conductor wire may be in contact with a metal portion such as the core to cause a short circuit, thereby lowering the reliability and durability of the electroacoustic transducer.
It may be contemplated to provide an additional part around which a conductor wire is to be wound. In this case, the production cost is increased by the additional part, and a step of attaching the additional part is additionally required.
Moreover, the additional part reduces the capacity of the back space of the electroacoustic transducer. Accordingly, the sound pressure characteristic, particularly that in the bass region is lowered.
SUMMARY OF THE INVENTION
The invention has been made in view of these problems. It is an object of the invention to provide an electroacoustic transducer in which, during a step of placing a coil, a conductor wire can be prevented from being damaged without increasing the production cost and the manufacturing steps and reductions in reliability and durability can be suppressed.
According to an aspect of the invention, there is provided an electroacoustic transducer comprising:
a pole piece having a base and a core;
a coil disposed around the core;
a magnet disposed around the coil; and
a case made of a resin material, the case accommodating the pole piece, the coil, and the magnet in an internal space thereof,
wherein a bobbin portion is formed integrally with the case, the bobbin portion elongating toward the internal space of the case; and
the coil is configured by winding a conductor wire around the bobbin portion.
In the electroacoustic transducer of the invention, the bobbin portion is formed integrally with the case which is made of a resin material, and the conductor wire is wound around the bobbin portion to configure the coil. Since the bobbin portion is made of the same resin material as the case, it is possible to prevent the conductor wire (covering layer thereof) from being damaged during a step of winding the conductor wire around the bobbin portion. This configuration prevents a short circuit possibly caused by a damaged conductor wire (coil) being in contact with a metal portion such as the core, and hence it is possible to suppress reductions of the reliability and durability of the electroacoustic transducer.
In the electroacoustic transducer of the invention, since the bobbin portion is formed integrally with the case, another member for winding the conductor wire is not additionally required. Therefore, it is possible to realize simply and at a low cost a configuration in which the bobbin portion can be provided without increasing the production cost and the manufacturing steps, and the conductor wire (covering layer thereof) can be prevented from being damaged.
Preferably, the case comprises an upper case, and a lower case having a coil terminal portion to which an end of the conductor wire is electrically connected, and the bobbin portion is formed integrally with the lower case.
Since the case is configured in this way, the bobbin portion which extends into the internal space of the case can be easily formed.
Preferably, the bobbin portion extends from the lower case to surround the outer periphery of the core, and the base is placed on the lower case, and has a hole through which the bobbin portion is passed.
Since the bobbin portion is formed in this way, it is possible to realize very simply a configuration in which the base can be easily placed on the lower case without interfering with the bobbin portion.
According to another aspect of the present invention, there is provided an electroacoustic transducer comprising:
a pole piece having a base and a core;
a bobbin portion placed to surround an outer periphery of the core;
a coil formed of a conductor wire wound around the bobbin portion; and
a magnet placed around the coil,
wherein the bobbin portion is divided into a plurality of portions along a circumferential direction of the core.
In the electroacoustic transducer of the invention, since the coil is configured by winding the conductor wire around the bobbin portion, it is possible to prevent the conductor wire (covering layer thereof) from being damaged during a step of winding the conductor wire. This configuration prevents a short circuit possibly caused by a damaged conductor wire (coil) being in contact with the core. As a result, it is possible to suppress reductions of the reliability and durability of the electroacoustic transducer.
In the electroacoustic transducer of the invention, since the bobbin portion is divided into plural parts along the circumferential direction of the core, the bobbin portion is intermittently placed as viewed along the circumferential direction of the core, and hence the capacity of the bobbin portion can be reduced. Therefore, a reduction of the capacity of the back space of the electroacoustic transducer can be suppressed as far as possible, so that the sound pressure characteristic can be prevented from being lowered.
Preferably, the transducer further comprises a case comprising: an upper case; and a lower case having a coil terminal portion to which an end of the conductor wire is electrically connected, and the bobbin portion is formed integrally with the lower case.
Since the transducer further comprises a case configured in this way, another part for winding the conductor wire is not additionally required. Therefore, it is possible to realize simply and at a low cost a configuration in which the bobbin portion can be disposed without increasing the production cost and the manufacturing steps, and the conductor wire (covering layer thereof) can be prevented from being damaged.
Preferably, the bobbin portion extends from the lower case to surround the outer periphery of the core, and the core is pressed against the bobbin portion. Since the bobbin portion is formed in this way, the pole piece can be prevented from being detached from the lower case.
Preferably the base is placed on the lower case, and has a hole through which the bobbin portion is passed. Accordingly, it is possible to realize very simply a configuration in which the base can be easily placed on the lower case without interfering with the bobbin portion.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a perspective view showing the whole appearance of an electroacoustic transducer according to an embodiment of the invention.
FIG. 2
is a section view showing the electroacoustic transducer according to the embodiment of the invention.
FIG. 3
is an exploded perspective view showing the configuration of the electroacoustic transducer according to the embodiment of the invention.
FIG. 4
is a plan view of a pole piece included in the electroacoustic transducer according to the embodiment of the invention.
FIG. 5
is a perspective view of the pole piece included in the electroacoustic transducer according to the embodiment of the invention.
FIG. 6
is a plan view of a lower case included in the electroacoustic transducer according to the embodiment of the invention.
FIG. 7
is a perspective view of the lower case included in the electroacoustic transducer according to the embodiment of the invention.
FIG. 8
is a plan view showing a state where electroacoustic transducer where a conductor wire is wound around a bobbin portion to constitute a coil.
FIG. 9
is a perspective view showing the state where the conductor wire is wound around the bobbin portion to constitute the coil.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
The present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the identical components are denoted by the same reference numerals, and duplicated description is omitted.
FIG. 1
is a perspective view showing the whole appearance of an electroacoustic transducer of the embodiment of the invention.
FIG. 2
is a section view showing the electroacoustic transducer.
FIG. 3
is an exploded perspective view showing the configuration of the electroacoustic transducer.
The electroacoustic transducer T has a case
1
made of a thermoplastic resin. The case
1
includes an upper case
11
and a lower case
21
which are bonded and fixed to each other by using the ultrasonic welding technique. The upper case
11
has a substantially box-like shape in which the lower face is opened. The upper case
11
has a sound release opening
12
in the upper face thereof and a sound release tube
13
extending toward the inside thereof. The upper case
11
has a stepped portion
14
against which an ultrasonic welder is to abut. A pole piece
31
, a coil
41
, a magnet
51
, a diaphragm
61
, and others are housed in the internal space defined by the upper case
11
and the lower case
21
.
The pole piece
31
is placed on the lower case
21
. As shown in
FIGS. 4 and 5
, the pole piece
31
has a core
32
having a substantially columnar shape, and a base
33
made of a metal material (for example, permalloy). The core
32
is caulked and integrally fixed to the center position of the base
33
. A cutaway portion
34
is formed in a predetermined position of the edge of the base
33
. A plurality of holes
35
(three in the embodiment) are formed in the base
33
so as to surround the portion to which the core
32
is fixed. A bobbin portion
24
that will be described later is to be passed through the plurality of holes
35
. In the embodiment, the base
33
is set to have a thickness of about 0.6 mm, and the length (the height) of the core
32
from the upper face of the base
33
is set to be about 3.8 mm.
As shown in
FIGS. 6 and 7
, integrally formed on the upper face of the lower case
21
are a wall
22
for defining the placement position of the pole piece
31
, a projection
23
engageable with the cutaway portion
34
of the base
33
, and the bobbin portion
24
for configuring the coil
41
. Formed at the wall
22
are projections
25
being engageable with a projection
15
formed on the upper case
11
. When the projections
25
and
15
are engaged with each other, the upper case
11
is positioned with respect to the lower case
21
. Each of the wall
22
and the projection
23
is set to have a height larger than the thickness of the base
33
. In the embodiment, the height of the wall
22
is set to be about 1.2 mm, and that of the projection
23
to be about 0.8 mm.
The bobbin portion
24
extends from the upper face of the lower case
21
toward the internal space of the case
1
so as to surround the outer periphery of the core
32
. The bobbin portion is divided into plural parts (three in the embodiment) along the circumferential direction of the core
32
. The bobbin portion
24
is configured by basal parts
26
and elongated parts
27
. The basal parts
26
are set to have a height (in the embodiment, about 0.85 mm) larger than the thickness of the base
33
. The length of each elongated part
27
is set to have a value (in the embodiment, about 2.95 mm) at which the top of the core
32
protrudes from the end of the elongated part
27
in a state where the pole piece
31
is placed on the lower case
21
. The inner diameter of the bobbin portion
24
(the basal parts
26
) is set to have a value (in the embodiment, about 2.2 mm) approximately equal to the outer diameter of the core
32
.
The face of each basal part
26
on the side of the core
32
is curved so as to extend along the outer periphery of the core
32
. In each elongated part
27
, also both the face on the side of the core
32
, and the rear face (the face on the side where a conductor wire
42
is to be wound) are curved so as to extend along the outer periphery of the core
32
. The sectional area of the basal parts
26
is set to be larger than that of the elongated parts
27
. According to this configuration, it is possible to ensure the mechanical strength of the bobbin portion
24
, so that the bobbin portion
24
is prevented from being detached from the lower case
21
.
The pole piece
31
(the base
33
) is pressed from the above of the lower case
21
in a state where the bobbin portion
24
(the elongated parts
27
) is passed through the holes
35
of the base
33
to be positioned on the outer periphery of the core
32
, whereby the pole piece is fitted and placed into the lower case
21
. At this time, the positioning of the pole piece
31
with respect to the lower case
21
is performed by engaging the cutaway portion
34
of the base
33
with the projection
23
of the lower case
21
. Under a state where the pole piece
31
is fitted into the lower case
21
, the core
32
is pressed against the bobbin portion
24
because the inner diameter of the bobbin portion
24
(the basal parts
26
) is set to have a value which is approximately equal to the outer diameter of the core
32
. As a result, the pole piece
31
is hardly detached from the lower case
21
.
As shown also in
FIGS. 8 and 9
, the coil
41
is configured by winding the conductor wire
42
around the elongated parts
27
of the bobbin portion
24
, and placed on the basal parts
26
. In the embodiment, a copper wire of a diameter of about 60 μm is used as the conductor wire
42
. An insulating layer is disposed on the outer periphery of the copper wire. The height of the coil is set to a value (in the embodiment, about 2.9 mm) smaller than the length of each elongated part
27
.
The basal parts
26
are set to have a height larger than the thickness of the base
33
so that the coil
41
does not abut against the base
33
(the pole piece
31
). The bobbin portion
24
(the elongated parts
27
) is divided into the plural parts along the circumferential direction of the core
32
so that the bobbin portion
24
(the elongated parts
27
) is intermittently placed as viewed along the circumferential direction of the core
32
. The conductor wire
42
is linearly wound between the divided parts of the bobbin portion
24
.
In the lower case
21
, lead terminals
28
and
29
serving as terminals of the coil
41
are disposed in an integral manner by so-called “insert molding”. As shown in
FIGS. 8 and 9
, the ends of the conductor wire
42
constituting the coil
41
are passed over the projection
23
formed on the lower case
21
, and then drawn out through a cutaway portion
30
formed in the wall
22
, onto lands
28
a
and
29
a
of the lead terminals
28
and
29
, respectively. Under this state, the ends are soldered to the lands
28
a
and
29
a.
The cutaway portion
30
formed in the wall
22
is sealed by a silicone material (not shown).
Referring again
FIGS. 2 and 3
, the magnet
51
is configured by an annular plastic magnet, and placed on the side of the outer periphery of the coil
41
with a gap provided between the magnet and the coil
41
. The magnet
51
is placed against the base
33
of the pole piece
31
, and against the wall
22
of the lower case
21
, thereby restricting the placement position of the magnet.
A stepped portion
52
is formed in the magnet
51
. The diaphragm
61
is placed on the stepped portion
52
. In the embodiment, the magnet
51
functions also as a support member which supports the diaphragm
61
. A magnetic piece
62
, serving as an additional mass, is disposed in a center portion of the diaphragm
61
. The diaphragm
61
is caused to be attracted toward the magnet
51
by function of the static magnetic field of the magnet
51
. The upward movement of the diaphragm
61
is restricted by the stepped portion
14
of the upper case
11
.
A back space A is formed on the side of the back face of the diaphragm
61
. A resonant space B surrounded by the upper case
11
is formed on the side of the upper face of the diaphragm
61
. The resonant space B is opened to the outside through the sound release tube
13
formed on the upper case
11
, i.e., the sound release opening
12
.
Then, the operation of the electroacoustic transducer T of the invention will be described. In the electroacoustic transducer T, the base
33
, the core,
32
, the diaphragm
61
, and the magnet
51
constitute a magnetic circuit, and the static magnetic field generated by the magnet
51
acts on the diaphragm
61
, so that the magnetized diaphragm
61
is attracted toward the core
32
. The magnet
51
functions so as to generate a bias magnetic field for the diaphragm
61
.
In contrast to the unidirectional magnetic field due to the static magnetic field, when an electric signal in the form of AC, pulses or the like is applied between the lead terminals
28
and
29
, the signal current flows through the coil
41
, and an oscillating magnetic field corresponding to the electric signal is generated in the core
32
. When the direction of the oscillating magnetic field is opposite to that of the static magnetic field of the magnet
51
, the diaphragm
61
swings in the direction away from the core
32
. When the direction of the oscillating magnetic field coincides with that of the static magnetic field, the diaphragm is attracted toward the core
32
. Such mechanical vertical movements depend on the frequency of the electric signal, with the result that the diaphragm
61
vibrates to cause air to oscillate. This oscillation is amplified as a resonant sound by the resonant space B. This sound is released mainly through the sound release opening
12
to the outside.
In the embodiment, as described above, the bobbin portion
24
(the basal parts
26
and the elongated parts
27
) is formed integrally with the lower case
21
(the case
1
) made of a resin material (thermoplastic resin), and the conductor wire
42
is wound around the bobbin portion
24
(the elongated parts
27
), whereby the coil
41
is configured. It is possible to prevent the conductor wire
42
, particularly the covering layer (insulating layer) thereof from being damaged during a step of winding the conductor wire
42
around the bobbin portion
24
(the elongated parts
27
), since the bobbin portion
24
(the elongated parts
27
) is made of the same resin material as the lower case
21
(the case
1
). As a result, this prevents a short circuit possibly caused by a damaged conductor wire
42
(coil
41
) being in contact with a metal portion such as the core
32
. It is possible to suppress reductions in reliability and durability of the electroacoustic transducer T.
The bobbin portion
24
(the basal parts
26
and the elongated parts
27
) and the lower case
21
(the case
1
) can be molded at one time because the bobbin portion
24
(the basal parts
26
and the elongated parts
27
) is formed integrally with the lower case
21
(the case
1
). Accordingly, Another part for winding the conductor wire
42
is not additionally required. Therefore, it is possible to realize simply and at a low cost a configuration in which the bobbin portion
24
can be disposed without increasing the production cost and the manufacturing steps, and the conductor wire
42
(covering layer thereof) can be prevented from being damaged.
Since the bobbin portion
24
(the basal parts
26
and the elongated parts
27
) is divided into plural parts along the circumferential direction of the core
32
, the bobbin portion
24
(the basal parts
26
and the elongated parts
27
) is intermittently placed as viewed along the circumferential direction of the core
32
, and hence the capacity of the bobbin portion
24
can be reduced. Therefore, a reduction of the capacity of the back space A of the electroacoustic transducer T can be suppressed as far as possible, so that the sound pressure characteristic can be prevented from being lowered.
Moreover, the conductor wire
42
is linearly wound between the divided parts of the bobbin portion
24
(the elongated parts
27
). According to this configuration, even when vibrations of any kind are transmitted to the coil
41
as in the case where the upper case
11
and the lower case
21
are ultrasonic welded together, movement of the coil
41
around the bobbin portion
24
is restricted, including a movement of the coil
41
toward the center axis of the core
32
. As a result, it is possible to prevent the conductor wire
42
constituting the coil
41
, from being damaged or broken.
The case
1
comprises the upper case
11
; and the lower case
21
in which the lead terminals
28
and
29
are disposed. The bobbin portion
24
(the basal parts
26
and the elongated parts
27
) is formed integrally with the lower case
21
, the bobbin portion
24
(the basal parts
26
and the elongated parts
27
) and the lower case
21
(the case
1
) can be molded at one time, and hence another part for winding the conductor wire
42
is not additionally required. Therefore, it is possible to realize simply and at a low cost a configuration in which the bobbin portion
24
can be provided without increasing the production cost and the manufacturing steps, and the conductor wire
42
(covering layer thereof) can be prevented from being damaged.
The bobbin portion
24
(the basal parts
26
and the elongated parts
27
) is extends from the lower case
21
so as to surround the outer periphery of the core
32
, and the core
32
is pressed against the bobbin portion
24
. Therefore, the pole piece
31
can be prevented from being detached from the lower case
21
, by the simple configuration.
The base
33
of the pole piece
31
has the holes
35
through which the bobbin portion
24
(the basal parts
26
and the elongated parts
27
) is to be passed. When the pole piece
31
is fitted and placed into the lower case
21
, therefore, the bobbin portion
24
(the basal parts
26
and the elongated parts
27
) does not interfere with the base
33
. As a result, it is possible to realize very simply a configuration in which the pole piece
31
can be easily placed on the lower case
21
.
The invention is not restricted to the embodiment described above. The above-mentioned values, and the shape of each component, and the like (for example, the shape and number of divisions of the bobbin portion
24
) can be set with being suitably changed. In the embodiment, the bobbin portion
24
is configured by the basal parts
26
and the elongated parts
27
. The configuration of the bobbin portion is not limited thereto. Alternatively, the bobbin portion may be configured by only parts corresponding to the elongated parts
27
.
In the embodiment, the bobbin portion
24
is formed integrally with the lower case
21
(the case
1
). The invention is not restricted thereto. For example, the bobbin portion
24
may be formed separately from the lower case
21
(the case
1
), and then attached and fixed to the lower case
21
by bonding or the like.
In the embodiment, the pole piece
31
is placed on the lower case
21
by means of fitting. The manner of the placement is not restricted thereto. For example, the pole piece
31
may be disposed integrally on the lower case
21
by the insert molding in the same manner as the lead terminals
28
and
29
. In this case, the bobbin portion
24
is formed so as to cover the outer periphery of the core
32
of the pole piece
31
.
As described above in detail, according to the invention, it is possible to provide an electroacoustic transducer in which, during a step of placing a coil, a conductor wire can be prevented from being damaged, without increasing the production cost and the manufacturing steps, and reductions in reliability and durability can be suppressed.
Claims
- 1. An electroacoustic transducer comprising:a pole piece having a base and a core; a bobbin portion placed to surround an outer periphery of the core; a coil formed of a conductor wire wound around the bobbin portion; and a magnet placed around the coil, wherein the bobbin portion is divided into a plurality of unattached individual portions along a circumferential direction of the core.
- 2. The electroacoustic transducer according to claim 1, wherein the transducer further comprises a case comprising:an upper case; and a lower case having a coil terminal portion to which an end of the conductor wire is electrically connected, and the bobbin portions are formed integrally with the lower case.
- 3. The electroacoustic transducer according to claim 2, wherein the bobbin portions extend from the lower case to surround the outer periphery of the core, andthe core is pressed against the bobbin portions.
- 4. The electroacoustic transducer according to claim 3, wherein the base is placed on the lower case, and has holes through which the bobbin portions are passed.
- 5. The electroacoustic transducer according to claim 2, wherein the base is placed on the lower case, and has holes through which the bobbin portions are passed.
Priority Claims (2)
Number |
Date |
Country |
Kind |
P. 2000-382286 |
Dec 2000 |
JP |
|
P. 2000-382297 |
Dec 2000 |
JP |
|
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Feb 1942 |
A |
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Olson et al. |
Jan 1955 |
A |
5394479 |
Ishigaya et al. |
Feb 1995 |
A |
5894263 |
Shimakawa et al. |
Apr 1999 |
A |
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Apr 1996 |
EP |
3-240399 |
Oct 1991 |
JP |
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Jan 1996 |
JP |
8-186895 |
Jul 1996 |
JP |
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